Tenth International Fermi Symposium

9 Oct 2022, 12:00 → 15 Oct 2022, 14:00 Africa/Johannesburg

Soebur Razzaque (University of Johannesburg), Elizabeth Hays (NASA GSFC), Markus Boettcher (North-West University), Judy Racusin (NASA/GSFC)

The Tenth International Fermi Symposium will be held in person at the Misty Hills Country Hotel, Conference Centre and Spa from the 9th-15th of October 2022. 

This symposium follows previous Fermi Symposia at Stanford, CA (February 2007), Washington, DC (November 2009), Rome, Italy (May 2011), Monterey, CA (November 2012), Nagoya, Japan (October 2014), Arlington, VA (November 2015), Garmisch-Partenkirchen, Germany (October 2017), Baltimore, MD (October 2018) and virtually, due to COVID-19 pandemic (April 2021). 

The two Fermi instruments have been surveying the high-energy sky since August 2008. The Large Area Telescope (LAT) has discovered more than a thousand new sources and many new source classes, bringing the importance of gamma-ray astrophysics to an ever-broadening community. The LAT catalog includes supernova remnants, pulsar wind nebulae, pulsars, binary systems, novae, several classes of active galaxies, starburst galaxies, normal galaxies, and a large number of unidentified sources. Continuous monitoring of the high-energy gamma-ray sky has uncovered numerous outbursts from a wide range of transients. Fermi LAT's study of diffuse gamma-ray emission in our galaxy revealed giant bubbles shining in gamma rays. The direct measurement of a harder-than-expected cosmic-ray electron spectrum may imply the presence of nearby cosmic-ray accelerators. LAT data have provided stringent constraints on new phenomena such as supersymmetric dark-matter annihilations as well as tests of fundamental physics. The Gamma-ray Burst Monitor (GBM) continues to be a prolific detector of gamma-ray transients: magnetars, solar flares, terrestrial gamma-ray flashes and gamma-ray bursts at keV to MeV energies, complementing the higher energy LAT observations of those sources in addition to providing valuable science return in their own right.

All gamma-ray data are made immediately available at the Fermi Science Support Center. These publicly available data and Fermi analysis tools have enabled a large number of important studies. We especially encourage guest investigators worldwide to participate in this symposium to share results and to learn about upcoming opportunities.

This meeting will focus on the new scientific investigations and results enabled by Fermi, the mission and instrument characteristics, future opportunities, and coordinated observations and analyses.

Indico Help Guide .pdf

Monday 10 October

09:00 → 10:30 Opening

Convener: Soebur Razzaque

09:00 Opening Remarks - 1

Speaker: Soebur Razzaque

Opening_remarks_2022.pdf

09:15 Opening Remarks - 2

Speaker: Markus Boettcher

SA-GAMMA_Fermi2022_Welcome.pdf

SA-GAMMA_Fermi2022_Welcome.pptx

09:30 Fermi Mission Talk

Speaker: Judy Racusin (NASA/GSFC)

Mission_Status_Fermi_Symposium_2022.pdf

Mission_Status_Fermi_Symposium_2022.pdf

10:00 Diversity and Equity in the Multimessenger Era

Multimessenger astronomy relies on the principles of cooperation and collaboration to make previously impossible discoveries. The Multimessenger Diversity Network (MDN) is applying these same principles to increasing diversity, equity, inclusion, and accessibility (DEIA) in the field. The MDN, a community of practice with a dozen participating collaborations, focuses on improving DEIA within collaborations themselves with the intent of improving the environment in which multimesenger astronomy is conducted. This talk will review the current state of DEIA in multimessenger astronomy, highlight the role and work of the MDN, and provide examples of efforts underway to improve DEIA in the field.

Speaker: Ellen Bechtol (UW-Madison / WIPAC)

FermiSymposium_EDI.pdf

10:30 → 11:00 Coffee Break

Posters

11:00 → 13:00 Plenary 1: Results from Arrays and Campaigns

Convener: Markus Boettcher

11:00 Optical Follow-up of X-ray and Gamma-ray Transients

I review the optical follow-up programme on high energy (X-ray and $\gamma$-ray) transient and variable sources, focusing on results from the Southern African Large Telescope (SALT) but also including supporting observations using SAAO and other facilities. This programme began in 2016 and various classes of objects have been observed, including $\gamma$-ray flaring blazars, high and low mass X-ray binaries, cataclysmic variables and changing-look AGN. This work has been supplemented with supporting multi-wavelength observations with other facilities (e.g. Fermi, Swift, eROSITA, NICER, HXMT, XMM-Newton, HESS and MeerKAT). I will highlight results covering different classes of objects, particularly focusing on LMXB black hole transients, transitional millisecond pulsars, white dwarf “pulsars” and X-ray QPE discoveries following from the eROSITA survey. Future prospects of transient follow-up in the era of the Rubin Observatory’s LSST will also be discussed.

Speaker: David Buckley (South African Astronomical Observatory)

Buckley-Fermi.pdf

Buckley-Fermi.pptx

11:30 Radio Astronomy in South Africa

The South African Radio Astronomy Observatory (SARAO) operates and is host to several radio telescopes, including the 64-dish MeerKAT Array. I'll give a brief overview of SARAO and its activities. The MeerKAT telescope, inaugurated in 2018, and still undergoing commissioning of advanced capabilities, has already proven its worth in the scientific arena. A brief overview of the MeerKAT science programme will be given, as well as science highlights of interest to the Fermi community. Technical capabilities, challenges in data reduction and how to apply for time will be discussed.

Speaker: Sharmila Goedhart (South African Radio Astronomy Observatory)

Radio astronomy in South Africa.pdf

12:00 EHT observations of the supermassive black hole in the Galactic Center

On 12 May 2022, the Event Horizon Telescope Collaboration published the first horizon-scale images of Sagittarius A*, the 4-million Solar mass black hole in the center of our Milky Way. These images were the result of a 230 GHz VLBI observing campaign with the Event Horizon Telescope in 2017, including extensive multi-wavelength coverage from other observatories. In this talk, I will give an overview of the observations, data analysis, and interpretation of the results. I will also provide a glimpse of the future of black hole imaging, in which the African continent may play a significant role.

Speaker: Freek Roelofs

freekroelofs_eht_link_to_google_slides

13:00 → 14:00 Lunch

14:00 → 15:30 Plenary 2: Galactic Sources

Convener: Andrzej Zdziarski

14:00 The Crab Nebula：an electron PeVatron or super Pevatron of cosmic rays?

Detection of 1.1 PeV photons from the Crab poses challenges to even classical electrodynamic theory and pure magnetohydrodynamics. Or, an accelerator that boosts protons to at highest energy of 30 PeV may be at the center of the nebula? LHAASO has found the most fascinating object, which was recorded as the first recognized supernova by Chinese in Song dynasty, so attractive that it may hint the origin of cosmic rays above the knee or an extreme electron accelerator with the acceleration rate approaching 1. More statistics is needed to unveil it. LHAASO's observation is updated.

Speaker: Zhen Cao (Institute of High Energy Physics, CAS, China)

14:30 Revealing time-resolved hadronic particle acceleration in the recurrent nova RS Ophuichi with H.E.S.S.

Recurrent Novae (RNe) are known to experience multiple eruptions in the form of thermonuclear explosions, due to the accumulation of material accreted by a white dwarf from a binary companion star.
The well known RN RS Ophiuchi (RS Oph) underwent its latest eruption in 2021 and triggered numerous follow-up observations world wide, including with the High Energy Stereoscopic System (H.E.S.S.), an array of Imaging Atmospheric Cherenkov Telescopes.

Non-thermal emission up to TeV energies is observed coincident with the Nova eruption within the first days and up to a month after the optical peak, establishing novae as Galactic transients reaching TeV energies.
Analysis and interpretation of the data identifies time-resolved acceleration of cosmic-rays, constraining models of particle energisation.

Combining the data taken by H.E.S.S. with concurrent observations taken by the Fermi-LAT, a similar temporal profile is observed, favouring a common origin to the emission.
In this talk, the detection of the non-thermal VHE emission from the RN RS Oph by H.E.S.S. will be presented and plausible models for the VHE emission discussed.

Speaker: Stefan Wagner

fermi22_RSOph_SW.pdf

15:00 Evidence of hadronic origin of the gamma-ray emission from the nova RS Oph by the MAGIC telescopes

RS Ophiuchi (RS Oph) is a symbiotic recurrent nova that shows eruptive events roughly every 15 years. On August 8th, 2021, RS Oph erupted with its latest outburst. This event was detected by a wide range of multi-wavelength (MWL) instruments from radio up to very-high-energy (VHE) gamma rays. The MAGIC telescopes followed up on optical and high-energy triggers and initiated an observation campaign from August 9th till September 1st. RS Oph is the first nova detected in the VHE gamma-ray energy range. We report on the detection of VHE gamma rays at a significant level of 13.2σ during the first 4 days of RS Oph with the MAGIC telescopes. We combine the VHE emission detected by MAGIC with optical and high energy observations and conclude RS Oph accelerated hadrons during its eruption. We will present the MWL modeling revealing this hadronic emission, and its further implications for Galactic cosmic-rays.

Speaker: David Green

Fermi_Symposium_RS_Oph_DGreen_v5.pdf

15:15 Pursuing gamma-ray emitting pulsar wind nebulae with the Fermi-LAT

Pulsars are rapidly rotating neutron stars that descend from a core collapse supernova and can generate pulsar wind nebulae (PWNe) through the expenditure of their rotational energy. PWNe are highly magnetized particle winds and are brightly detected across the electromagnetic spectrum. Synchrotron emission from the relativistic particles is observed from the majority of these objects from radio to X-ray while the same particle population is believed to scatter off of ambient photon fields generating Inverse Compton Scattering (ICS) emission at gamma-ray energies. Gamma-rays are becoming key to finding and characterizing PWNe. In fact, the majority of Galactic TeV sources detected by Imaging Air Cherenkov Telescopes are classified as PWNe. However, the Fermi—LAT has only identified a small fraction of MeV—GeV PWN counterparts, due to most PWN locations being along the Galactic plane, embedded within bright diffuse gamma-ray emission. A systematic search in the 11.5yr Fermi—LAT dataset is presented. The locations of PWNe identified in other wavelengths are targeted, omitting systems that have pulsars detected by the Fermi—LAT for the first half of the search. We present the preliminary results for the Fermi—LAT analysis of 58 regions accompanied by the broadband analyses of two newly detected Fermi PWNe and the physical implications of the results.

Speaker: Jordan Eagle (Goddard Space Flight Center)

10th_fermi_intl_symposium2022.pdf

10th_fermi_intl_symposium2022.pptx

15:30 → 16:00 Coffee Break

Posters

16:00 → 17:30 Parallel 1: Pulsar I

Convener: Christo Venter

16:00 Joint Pulsar Studies with the FAST Radio Telescope and the Fermi LAT

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese megascience facility built by the National Astronomical Observatories (NAOC) of the Chinese Academy of Sciences (CAS). Completed in 2016, FAST is the world's largest single-dish radio telescope, and is currently operating as an international facility, with regular proposal calls open to observers from around the world. In December 2017, an MOU between FAST and the Fermi LAT Collaboration was signed, with the goal of sharing expertise and resources in the interest of facilitating joint pulsar studies with both observatories. This has led to a number of discoveries, including PSR J0318+0253, the high-energy MSP with the faintest ever detected radio pulsations. Indeed, the superb sensitivity of FAST has enabled the deepest radio searches to date of a number of systems suspected of hosting pulsars, in some cases revealing previously undetected radio pulsations. In addition, the Commensal Radio Astronomy FAST Survey (CRAFTS) has led to the discovery of more than 170 new radio pulsars, some of which have subsequently been shown to be gamma-ray emitters. In this talk I will summarize some of the key results from the FAST/Fermi-LAT collaboration, and give an update on the status of various ongoing observing proposals.

Speaker: Dr Pablo Saz Parkinson (University of California, Santa Cruz)

221010_Saz_Parkinson_10thFSymp_opt.pdf

16:15 _

16:30 The high-energy gamma-ray emission of globular clusters

There are now 35 confirmed gamma-ray bright globular clusters (GCs) in the Milky Way. The millisecond pulsar (MSP) populations within these clusters are widely considered to be their primary source of gamma-ray emission. There are two proposed mechanisms for high-energy gamma-rays to be created in GCs by MSPs. The first is radiation from charged particles traveling along the open magnetic field lines of the pulsar, and the second is inverse Compton scattering (ICS) due to charged relativistic particles from the MSP upscattering starlight and CMB photons. The degree to which the ICS component contributes to GC gamma-ray emission is currently unknown. In this talk, I will discuss recent efforts by myself and collaborators to further understand the high-energy gamma-ray emission of GCs using data from both Fermi-LAT and the High Altitude Water Cherenkov (HAWC) experiment. In particular, we search for evidence of ICS emission from the M54 globular cluster at the center of the Sagittarius dwarf galaxy. As we find only what appears to be prompt emission from an unseen population of MSPs within the cluster, we report upper limits on its ICS flux and test our methodology on other GCs with a possible ICS component. We successfully recover the ICS component of Terzan 5's spectral energy distribution; a GC which is known to have high-energy gamma-ray emission. Finally, we search for evidence of other gamma-ray sources associated with Sagittarius and compare our results to the total population of gamma-ray GCs.

Speaker: Addy Evans

Evans_FermiSymposium.pdf

16:45 Origin of pulsar radio emission

For more than five decades, the origin of pulsar radio emission have been one of the
major unsolved problems in astrophysics. It is universally believed that generation
of radio emission is intimately connected with pair plasma production initiated by
high energy gamma-rays in pulsar polar caps. Here I will present the results of our
study of electron-positron pairs creation near magnetic poles of neutron stars which
provide a clue to this long-standing mystery. We directly demonstrate that the
intermittency of the pair creation process and its naturally-arising non-uniformity
across magnetic field lines lead to the emission of strong coherent electromagnetic
waves with properties commensurate with that of the observed pulsar radio
emission. These waves are only moderately damped by dense plasma and should escape
the magnetosphere and be observable as coherent radio emission. Our findings may lay
the theoretical foundation for the interpretation of a plethora of observational
phenomena seen in radio pulsars, magnetars, and possibly FRBs.

Speaker: Andrey Timokhin (University of Zielona Góra)

timokhin_Fermi_2022.pdf

17:00 _

17:15 Constraining the multipolar magnetic field of millisecond pulsar PSR J0030+0451 via NICER X-ray light curve fitting

The Neutron star Interior Composition Explorer (NICER) has been operating since 2017 with the major aim of gaining a better understanding of the extreme nature of neutron stars (NSs). With its exceptional sensitivity, it hopes to constrain the equation of state of NSs to high precision. Modelling thermal X-ray light curves (LCs) of pulsars can provide us with insights into the magnetic field structure of an NS and the morphology of the surface hot spots.

Recent studies strongly indicate a multipolar magnetic field for the millisecond pulsar PSR J0030+0451 using NICER data, while constraining the parameter space for the field configuration. We are refining the offset dipole+quadrupole model of Kalapotharakos et al. (2021), by including a multipolar magnetic field configuration, going up to an l=3 component, and using Markov chain Monte Carlo (MCMC) methods to fit the NICER X-ray LCs.

Exploring the general magnetic multipolar parameter space using MCMC would help us constrain the field structure, and eventually the stellar mass and radius more robustly. In this talk, the optimal multipolar field configuration and an exploration of the MCMC parameter space will be shown.

Speaker: Anu Kundu

Kundu_Fermi_Symposium_2022.pdf

16:00 → 17:30 Parallel 2: SNR/PWNe

Convener: Pieter Meintjes (University of the Free State)

16:00 X and gamma ray correlations in the SNR RX J1713.7-3946

RX J1713.7-3946 is the brightest TeV supernova remnant, so it is an important test case for cosmic-ray acceleration. The mainstream view is that the SNR developed into the tenuous wind of its high-mass progenitor and now reaches a shell of denser gas around. The gamma rays are well correlated with the X-rays (synchrotron), but the correlation is very non linear (approximately Fgamma as Sqrt(FX)). The most natural model (Acero et al 2009, A&A 505, 157) is that gamma rays are dominated by inverse Compton emission (leptonic).
We have obtained deep full coverage of RX J1713.7-3946 with XMM-Newton (PI F. Acero), increasing the exposure by a factor of up to 8 and revealing faint structures in an unprecedented way. Together with the good TeV map (HESS collaboration et al 2018, A&A 612, A6), it allows testing the gamma/X correlation into the faint areas. The HESS collaboration reported gamma-ray emission beyond the X-ray border in the southwest, which could be due to escape of cosmic-ray protons. We revisit these radial profiles taking into account the absorption effect in the X-rays and the gamma/X correlation. We also find a nice example of clump/shock interaction.

Speaker: Jean Ballet

JBallet_RXJ1713_v3.pdf

16:15 Comparisons of astrometric GeV and TeV observations

While gamma-ray instruments have notoriously poorer imaging quality than most instruments used at lower energies, dedicated techniques have been developed to push the angular resolution to the limits. Many SNR and plerions have been spatially resolved in the VHE band with the HESS array. We will present matching studies with LAT data, compare the astrometric and morphological results in adjacent and overlapping energy bands and will discuss astrophysical conclusions in the light of consistency and systematics for several SNR and PWN. We conclude that astrometric constraints allow us to constrain radiation mechanisms.

Speaker: Prof. Stefan Wagner (LSW, ZAH, U Heidelberg.)

fermi22_Crab_SW.pdf

16:30 Study of maximum electron energy of sub-PeV pulsar wind nebulae by multiwavelength modelling

Recently, the Large High Altitude Air Shower Observatory (LHAASO) reported discovery of 12 ultrahigh-energy (UHE; ε≥100 TeV) gamma-ray sources located in the Galactic plane. Few of these UHE gamma-ray emitting regions are in spatial coincidence with pulsar wind nebula (PWN) objects. We consider a sample of five sources; two of them are LHAASO sources (LHAASO J1908+0621 and LHAASO J2226+6057) and the remaining three are GeV-TeV gamma-ray emitters. In addition, their X-ray and radio observations or upper limits are also available for these objects. We study multiwavelength radiation from these sources by considering a PWN origin, where the emission is powered by time-dependent spin-down luminosity of the associated pulsars. In this one zone, time-dependent leptonic emission model, the electron population is calculated at different times under the radiative (synchrotron and inverse-Compton) and adiabatic cooling. We estimate the upper limits on the minimum Lorentz factor of the electrons and it also infers the minimum value of the pair-multiplicity of charged pairs. Further, the maximum value of the electron Lorentz factor is estimated by the maximum observed photon energy in the sub-PeV range. In the special case of HESS J1640-465, a higher energy density of the stellar photons is required to fit gamma-ray data compared to the standard IR/CMB background used in the PWNe modelling. We also discuss the possible modification in the model parameters, if the escape of particles is allowed from the pulsar wind nebula. For example, we consider LHAASO 1908+0621 and discuss qualitatively the impact of escape of particles from this source.

Speaker: Jagdish Joshi

UHE_gamma_rays_and_PWN_Emission.pdf

16:45 Gamma-ray emission from young supernova remnants in dense, structured circumstellar environments

Supernova remnants are known to accelerate cosmic rays from the detection of non-thermal emission of radio waves, X-rays, and gamma rays. The presence of cut-offs in the gamma-ray spectra of several young SNRs led to the idea that the highest energies might only be achieved during the very initial stages of a remnant’s evolution. Unfortunately, the gamma-ray luminosity is assumed to peak in the first weeks after the Supernova explosion where strong γγ-absorption attenuates the observable signal. Here, we investigate to which extend the interaction of SNR-shocks with dense structures in the medium around red supergiant (RSG) and luminous blue variable (LBV) stars can boost the gamma-ray emission months to years after the explosion.

We use the time-dependent acceleration code RATPaC to study the acceleration of cosmic rays in supernovae expanding into dense environments around massive stars. We performed spherically symmetric 1-D simulations in which we simultaneously solve the transport equations for cosmic rays, magnetic turbulence, and the hydrodynamical flow of the thermal plasma in the test-particle limit.

We investigated typical parameters of the circumstellar medium (CSM) in the freely expanding winds around RSG and LBV stars and added dense structures that arise from episodes of highly-enhanced mass-loss in case of LBV or photoionization-shells in the case of RSG progenitors.

We find that the interactions with the dense structures happens typically after a few months for LBV progenitors and a few years for RSG progenitors. During the interaction stage, the γγ-absorption by photons emitted from the Supernova’s photosphere became negligible. The gamma-ray luminosity of the interacting SNRs can surpass the internal/unabsorbed peak-luminosity that arises shortly after the explosion. As a consequence, the observable flux can be considerably higher compared to the signal expected shortly after the explosion where γγ-absorption is important and where most gamma-ray observatories search for transient signals from these Supernovae.

Speaker: Robert B.

Robert_Brose.pptx

17:00 Leptonic Nonthermal Emission from Supernova Remnants Evolving in the Circumstellar Magnetic Field

The very-high-energy gamma-ray emission observed from a number of Supernova remnants (SNRs) indicates particle acceleration to high energies at the shock of the remnants and a potentially significant contribution to Galactic cosmic rays. It is, however, difficult to determine whether protons (through hadronic interactions and subsequent pion decay) or electrons (through inverse Compton scattering on ambient photon fields) are responsible for this emission. For a successful diagnostic, a good understanding of the spatial and energy distribution of the underlying particle population is crucial. Most SNRs are created in core-collapse explosions and expand into the wind bubble of their progenitor stars. This circumstellar medium features a complex spatial distribution of gas and magnetic field which naturally strongly affects the resulting particle population. In this work, we conduct a detailed study of the spectro-spatial evolution of the electrons accelerated at the forward shock of core-collapse SNRs and their non-thermal radiation, using the RATPaC code that is designed for the time- and spatially dependent treatment of particle acceleration at SNR shocks. We focus on the impact of the spatially inhomogeneous magnetic field through the efficiency of diffusion and synchrotron cooling. It is demonstrated that the structure of the circumstellar magnetic field can leave strong signatures in the spectrum and morphology of the resulting non-thermal emission.

Speaker: Iurii Sushch (North-West University, South Africa)

Sushch_SNR_circumstellar_field_FermiSymp.pptx

17:15 SN 2016iyc: A Type IIb supernova arising from a low-mass progenitor

In this work, photometric and spectroscopic analyses of a very low-luminosity Type IIb supernova (SN) 2016iyc have been performed. SN 2016iyc lies near the faintest end among the distribution of similar supernovae (SNe). Given lower ejecta mass ($M_{\rm ej}$) and low nickel mass ($M_{\rm Ni}$) from the literature, combined with SN 2016iyc lying near the faintest end, one-dimensional stellar evolution models of 9 - 14 M$_{\odot}$ zero-age main-sequence (ZAMS) stars as the possible progenitors of SN 2016iyc have been performed using the publicly available code MESA. Moreover, synthetic explosions of the progenitor models have been simulated using the hydrodynamic evolution codes STELLA and SNEC. The bolometric luminosity light curve and photospheric velocities produced through synthetic explosions of ZAMS stars of mass in the range 12 - 13 M$_{\odot}$ having a pre-supernova radius $R_{\mathrm{0}} =$ (240 - 300) R$_{\odot}$, with $M_{\rm ej} =$ (1.89 - 1.93) M$_{\odot}$, explosion energy $E_{\rm exp} = $ (0.28 - 0.35) $\times 10^{51}$ erg, and $M_{\rm Ni} < 0.09$\,M$_{\odot}$, are in good agreement with observations; thus, SN 2016iyc probably exploded from a progenitor near the lower mass limits for Type IIb SNe.

Speaker: Amar Aryan

Amar_aryan_10thFSymp.pdf

Amar_aryan_10thFSymp.pdf

Amar_aryan_10thFSymp.pptx

Tuesday 11 October

09:00 → 10:30 Plenary 3: Pulsars

Convener: Patrizia Caraveo (INAF-IASF Milano)

09:00 Looking at the X-ray sky with polarized lenses

The Imaging X-ray Polarimetry Explorer (IXPE) is a joint NASA-ASI mission, launched on the 9th of December 2021 and entirely devoted to measuring the polarization of cosmic X-ray sources. Thanks to the innovative gas detectors positioned in the focal plane of its three, identical, X-ray telescopes, IXPE possesses the unprecedented capability of performing space, time and energy resolved polarimetry in the soft (2-8 keV) energy band.
During its first months of operations in space, IXPE has observed a variety of targets from different classes of emitters, pushing forward our understanding of these systems in many respects: by mapping the direction and level of ordering of the magnetic field in Supernova Remnants and Pulsar Wind Nebulae; by revealing the geometry of binary systems with neutron stars or black holes; by discriminating between different emission models for the jet of Active Galactic Nuclei; by probing the physics of light propagation in the extremely magnetized atmosphere of isolated pulsars. The perspective for future observations are equally bright, as the instrument continues to operate flawlessly, keeping intact its potential for discoveries as new targets are being observed.

Speaker: Alberto Manfreda

looking_at_x_ray_sky_with_polarized_lenses.pdf

09:30 The Galactic population of canonical pulsars

Current wisdom accounts the diversity of neutron star observational manifestations to their birth scenarios influencing their thermal and magnetic field evolution. Among the kind of observed neutron stars, radio pulsars represent by far the largest population of neutron stars.

In our work we aim at constraining the observed population of canonical neutron star period, magnetic field and spatial distribution at birth in order to understand the radio and high-energy emission processes in a pulsar magnetosphere. For this purpose we design a population synthesis method self-consistently taking into account the secular evolution of a force-free magnetosphere and the magnetic field decay.

We generate a population of pulsars and evolve them from their birth to the present time, working in the force-free approximation. We assume a given initial distribution for the spin period, surface magnetic field and spatial galactic location. Radio emission properties are accounted by the polar cap geometry whereas the gamma-ray emission is assumed to be produced within the striped wind model.

We found that a decaying magnetic field gave better agreement with observations compared to a constant magnetic field model. Starting from an initial mean magnetic field strength of $B=2.5\times 10^8$~T with a characteristic decay timescale of $4.6 \times 10^5~$yr, a neutron star birth rate of $1/70~$yr and a mean initial spin period of $60~ms$, we found that the force-free model satisfactorily reproduces the distribution of pulsars in the $P-\dot{P}$ diagram with simulated populations of radio-loud, radio-only and radio quiet gamma-ray pulsars similar to the observed populations.

More details about this work can be found here http://arxiv.org/abs/2206.13837

Speaker: Ludmilla Dirson

slides_10thFSymp.pdf

09:45 Interpreting the high-energy sub-exponentially cutoff spectral shape of the Vela pulsar

The Fermi Large Area Telescope (LAT) has detected over 270 pulsars in the GeV range. Their spectra are typically fit with hard power law functions with sub-exponential spectral cutoffs occurring in a narrow band around a few GeV. Recently, a debate ignited over the GeV emission mechanism. Traditionally, this component has been attributed to curvature radiation from the inner magnetosphere; in some later models, such emission predominantly takes place in the current sheet near the light cylinder. Alternatively, particles may be accelerated via magnetic reconnection in the current sheet and emit GeV photons via synchrotron radiation. The outer gap and separatrix/current sheet models both assume curvature or synchro-curvature emission as the mechanism responsible for GeV emission. It has been a challenge for traditional outer gap models to reproduce the sub-exponential GeV tails, while in slot gap / separatrix models, this comes about naturally due to the force-free-like magnetic field structure leading to a particular distribution of local curvature radii of the particle trajectories. In this talk, we present first results of our study of the phase-resolved GeV-band spectrum of the Vela pulsar, indicating the effect of different model parameters on the predicted spectral shape. We also indicate how gamma-ray emission from different heights contribute to the observed spectrum, leading to the build-up of the sub-exponential tail.

Speaker: Christo Venter

Venter_Fermi_SC.pdf

Venter_Fermi_SC.pptx

Venter_Fermi_SC.pptx

10:00 Searching for Gravitational Waves with Gamma Rays

Pulsar timing arrays (PTAs) are long-term monitoring campaigns of many millisecond pulsars (MSPs). Their key science goal is the detection and characterization of the few-nHz gravitational wave background (GWB) expected primarily from the mergers of supermassive black holes. These waves are random (stochastic), but the shared vantage point of the earth introduces hallmark correlations in the data which encode the strength and nature of the GW sources. The Fermi Large Area Telescope has detected more than 100 MSPs, and with its accurate and precise timestamping, it is a gamma-ray PTA. Sensitivity to the GWB increases dramatically with longer data sets, and we recently derived an independent upper limit on the GWB which is competitive with radio observing campaigns but free from many confounding effects, like propagation through the ionized interstellar medium. Here, we summarize these original results, give an update based on proposed improvements to the measurement precision, and discuss prospects for the eventual detection and characterization of the GWB.

Speaker: Matthew Kerr

10:30 → 11:00 Coffee Break

Posters

10:30 → 11:00 Poster session: Poster Session

AGN - GRBs - SNR/PWNe - Future Missions/Instruments - Analysis Techniques - Pulsars - Binaries - Neutrinos - Diversity and Equity - Dark Matter - Solar System Gravitational Waves

10:30 Inverse Compton emission from relativistic particles accelerated at shear layers in relativistic jets

Both observational evidence and theoretical considerations from MHD simulations of jets suggest that the relativistic jets of active galactic nuclei (AGN) are radially stratified, with a fast inner spine surrounded by a slower-moving outer sheath. The resulting relativistic shear layers are a prime candidate for the site of relativistic particle acceleration in the jets of AGN and gamma-ray bursts (GRBs). In this talk, we will present the results of particle-in-cell simulations of magnetic-field generation and particle acceleration in the relativistic shear boundary layers (SBLs) of jets in AGN and GRBs including the self-consistent calculation of the radiation spectrum produced by inverse Compton scattering of relativistic electrons in an external soft photon field.

Speaker: Mr Tej Bahadur Chand (Centre for Space Research, North-West University Potchefstroom, South Africa)

10:30 Multi-messenger characterization of Mrk501 during historically low X-ray and γ-ray activity

Blazars are among the brightest objects in the γ-ray sky. Nonetheless, even after decades of γ-ray and multiwavelength observations, they are far from being understood.
In this contribution, we introduce a multiwavelength data set of the archetypal blazar, Mrk 501. The data set spans the period from 2017 to 2020 and is complemented by a 12-year data set that starts in 2008 for some of the wavebands. This comprehensive data set allows us to, for the first time, identify significant correlations between HE γ-rays and X-rays that occur on both long (~year) and short (~days) time scales. These correlations support a leptonic scenario as the mechanism responsible for the variable part of the blazar's emission. Additionally, we find a significant correlation between the HE γ-ray and radio wavebands, with the radio lagging the γ-rays by at least 100 days.
In the most variable wavebands, very-high-energy (>0.2 TeV, VHE) γ-rays and X-rays, we identify a two-year period of historically low activity with stable VHE emission at the level of 5% that of the Crab Nebula. Using leptonic, hadronic or leptohadronic models to explain this possible baseline emission of Mrk 501, we can reproduce the observations, including public IceCube data. The baseline emission could be attributed to a standing shock, while the more variable emission could be connected to relativistic leptons accelerated by a traveling shock.

Speaker: Lea Alina Heckmann (Max-Planck-Institut für Physik, D-80805 München, Germany)

Poster_FermiSymp2022.pdf

10:31 Detection of transient quasi-periodic flux modulation at gamma-rays from blazar PKS 0903-57

We report the detection of a transient quasi-periodic flux modulation in the 6-hour binned $\gamma$-ray light curve of blazar PKS 0903-57 observed by Fermi-LAT. Several independent periodicity search analyses revealed a periodicity of $\sim$6 days that lasted for 5 full cycles during its outburst in March-April 2020. Using Monte-Carlo light curve simulation technique, we found the QPO detection significance to be 4.7$\sigma$. We explored a few physical models responsible for the observed transient QPO, such as a binary black hole system, precession of the jet, a hotspot rotating around the central black hole near the innermost stable circular orbit etc. The flaring episode can be explained as the emergence of a bright plasma blob close to the central engine. The periodic flux variation with a trend of decreasing peak flux can probably be attributed to the helical motion of the blob inside a curved jet.

Speaker: Mr ABHRADEEP ROY (Tata Institute of Fundamental Research, Mumbai, India)

Abhradeep_Fermi_poster_2022.pdf

10:31 Multi-wavelength study of blazars at redshift z>~1 observed by H.E.S.S.

We present the results of the multiwavelength study of several blazars at redshift z >~1 that have been observed by the High Energy Stereoscopic System (H.E.S.S.) since 2016 in target-of-opportunity observations, triggered by gamma-ray flaring states detected by the Fermi Large Area Telescope (LAT). We collect data from the Fermi-LAT, SWIFT and H.E.S.S. telescopes and model the broadband spectral energy distributions with both leptonic and hadronic models. The main goals of the project are to identify potential new very-high-energy g-ray blazars belonging to the low-synchrotron-peaked class of blazars and to constrain the evolution of the Extragalactic Background Light (EBL) at redshifts beyond z ~ 1. A detailed analysis, including multi-wavelength modelling, is presented for the flat-spectrum radio quasar CTA102 (z = 1.032). The source was not detected by H.E.S.S., providing upper limits at > 200 GeV g-rays. We used single-zone, steady-state leptonic and hadronic models to fit the SED of CTA102 and find that they provide acceptable fits. In both cases, the intrinsic spectrum (before EBL absorption) naturally cuts off at a few GeV, where EBL absorption is still negligible. Therefore, the H.E.S.S. upper limits for CTA102 do not allow us to draw conclusions concerning the EBL at redshift z ~ 1.
Keywords: Galaxies: active, radiation mechanism: non-thermal- relativistic process,
jets: quasars.

Speaker: Ogochukwu Chibueze (NORTH WEST UNIVERSITY, POTCHEFSTROOM, SOUTH AFRICA)

10:32 Flare States Modeling and Spectral Study of S5 1044+71

Blazars are a special kind of active galactic nuclei (AGNs) with jets oriented at small angles to our line of sight. Due to the relativistic motion of plasma along the jet, it constitutes one of the most rapidly varying classes of objects over a broad energy band (radio to γ-ray). S5 1044+71 (z = 1.15) is a known distant blazar observed in the GeV energy band. In the latest Fermi-LAT source catalog, 4FGL 1048.4+7143 is associated with S5 1044+71. Based on 12.5 years of good quality Fermi-LAT data, we have detected three long-term flaring activities of S5 1044+71. In this work, we report a detailed temporal and spectral study of all three long-term flares of S5 1044+71 which provides some insight into acceleration and emission mechanisms inside the jet. For the temporal study, we have decomposed Fermi data into two energy bands (0.1-0.4 and 0.4-300 GeV) and produced corresponding weekly binned Fermi light curves for all flares. The modelling of weekly binned light curves includes the rise and decay time analysis and study of flux-index correlation for each flare. We have also performed the correlation study and hardness ratio test between two energy bands. The temporal analysis provides a detailed evolutionary picture of flares over different energy bands. The multi-wavelength data were taken from different publicly available telescopes like SPOL-CCD of Steward Observatory, Swift-XRT and Swift-UVOT. As a part of the spectral study, broadband SEDs of three flares are modelled using a leptonic scenario with two emission zones where the second zone is only responsible for high energy emission. The modelling of broadband SED provides some insight into the intrinsic jet parameters which help us to understand the nature of different emission mechanisms inside the jet.

Speaker: Anshu Chatterjee (TATA INSTITUTE OF FUNDAMENTAL RESEARCH)

AChatterjee_Fermi_symposium_poster_id80.pdf

10:32 Multiwavelength study of 2020 and 2021 flares of S5 1803+784

We report the spectral and temporal analysis of S5 1803+784, a low synchrotron peaked (LSP) BL Lac object, during the 2020 and 2021 flaring states. The spectral energy distributions (SEDs) were studied in the framework of the single-zone leptonic jet model and broken power-law leptonic electron distribution. BL Lacertae objects (BL Lacs) high energy emissions can often be modelled as a single-zone emitting region undergoing synchrotron self-Compton (SSC) emission intrinsic to the jet, without the need for soft photons from sources external to the jet (external Compton or EC). However, the synchrotron+SSC-only emission may not be applicable to S5 1803+784, which has weak but observable optical emission lines. Fitting the multiwavelength spectral energy distribution (SED) to leptonic single-zone models can provide a constraint on the emitting region size and structure, the γ-ray emission process, and the possible driver of particle acceleration as well as the intrinsic jet parameters. A flare was reported on 12 April 2020 in the jet of S5 1803+784. We use two approaches to model the SEDs, namely, the SSC-only and SSC + EC scenarios during the flare using both multiwavelength simultaneous and archival data. We show that the X-ray emission during the flare in both cases is dominated by the upper tail of the synchrotron emission.
In contrast, the quiescent state is dominated by the low-energy part of the inverse-Compton component. The transition of the inverse Compton process from the Thomson regime (in the quiescent state) to the Klein Nishina regime in the flaring state as a result of the acceleration of the emitting particles is an interesting feature of S5 1803+785 during this flare. It could explain the high spectral curvature of the γ-ray emission. We show that in the quiescent state, the SSC + EC model is a statistically significant improvement over the SSC-only model, which indicates that external inverse Compton photons originating from the dusty torus (DT) may dominate the γ-ray emission in S5 1803+784.

Speaker: Joseph Omojola

S51803+784_poster_final.pdf

10:33 Radiation and polarization signatures from magnetic reconnection in blazars

Blazars are among the most powerful cosmic particle accelerators in our Universe. Strong multi-wavelength variability suggests extreme particle acceleration locally in the blazar emission region. Previous studies find that shock, magnetic reconnection, and turbulence can be the underlying particle acceleration mechanisms in the emission region. However, most theoretical models involve oversimplified assumptions and unconstrained parameters, diminishing the predictive power. Here we present combined particle-in-cell simulations with polarized radiation transfer. Our first-principle-integrated approach can derive all observables self-consistently with the minimal free parameters. We show that magnetic reconnection is characterized by strong variability in both flux and polarization. In particular, strong gamma-ray flares accompanied by optical polarization angle swings can be attributed to major plasmoid mergers in the reconnection layer, which may be a unique signature for magnetic reconnection. Future high-cadence optical polarization monitoring simultaneous with multi-wavelength light curves can help to identify reconnection in blazars.

Speaker: Dr Haocheng Zhang (NPP Fellow/NASA GSFC)

FermiSymposium2022Reconnection.pdf

FermiSymposium2022Reconnection.pptx

10:33 X-ray and MeV polarization signatures as a probe for hadronic signatures in blazars

Polarimetry is a direct measurement of the magnetic field in astrophysical objects. With the launch of IXPE, as well as future MeV polarimeters under development, such as COSI and AMEGO-X, multi-wavelength polarimetry will shed light on the magnetic field and particle acceleration in blazars. Here we present our theoretical predictions of multi-wavelength blazar polarization signatures. We find that in low-synchrotron-peaked and intermediate-synchrotron-peaked blazars, high X-ray polarization degree (comparable to or higher than the optical counterpart) can be strong evidence for neutrino production in the blazar emission region. Additionally, high MeV polarization degree can be unique signatures of proton synchrotron, implying that blazars can be the source of ultra-high-energy cosmic rays. For high-synchrotron-peaked blazars, time-resolved X-ray polarization variability can distinguish particle acceleration mechanisms such as magnetic reconnection and turbulence.

Speaker: Dr Haocheng Zhang (NPP Fellow/NASA GSFC)

FermiSymposium2022Hadronic.pdf

FermiSymposium2022Hadronic.pptx

10:34 Results from optical spectropolarimetric & photometric observations of blazars

At optical wavelengths, blazar SEDs show a superposition of non-thermal (polarised) emission from the jet, and thermal (unpolarised) emission from the accretion disc, broad-line region, dust torus and host galaxy itself. Due to their variability, the level of polarisation present in blazar emission changes as the non-thermal jet emission becomes more/less prominent. Hence, polarisation studies in blazars provide a direct link to jet activity, as well as a tool to disentangle the different emission components in blazar SEDs. Since 2016, as part of a ToO observation campaign with the Southern African Large Telescope (SALT), a selection of 18 blazars (10 FSRQs, 8 BLLs) have been observed during different states (low/quiescent or high/flaring) to trace the evolution of polarisation in its emission. The optical spectropolarimetry observations cover a wavelength range of λ ≈ 3500Å – 9000Å, with a resolution of R ≈ 170 – 530 (grating PG0300), or R ≈ 670 – 1040 (grating PG0900). The observations provide the optical spectra, and the degree of polarisation and polarisation angle as a function of wavelength. The observations have been complemented by quasi-contemporaneous photometric observations taken with the Las Cumbres Observatory (LCO) to improve flux calibration and study optical light curves. We present an overview of some results for this campaign.

Speaker: Joleen Barnard

10:34 SALT Spectropolarimetric Pipeline Comparisons

Blazars are active galactic nuclei with jets aligned very closely to our line of sight. The optical emission of blazars is often dominated by the polarised, non-thermal emission arising in the jet, with an underlying unpolarised, thermal emission component arising from the host galaxy, dusty torus, and accretion disk components. As the emission of blazars varies between flaring/high states and quiescence, the strength of the thermal and non-thermal emission components changes. Coupled with multi-wavelength observations, optical spectropolarimetry during both flaring and quiescent states can be used to disentangle the polarised and unpolarised components in the spectral energy distributions of blazars, providing better constraints for the non-thermal particle distribution. To this end, spectropolarimetry observations of a large selection of blazars during different states of activity were taken with the Southern African Large Telescope using the RSS. For RSS spectropolarimetry observations, the reduction, wavelength calibration, and extraction of the spectrum and calculation of the polarisation, is performed using the Polsalt pipeline. In order to facilitate the blazar observations we have developed a supplementary pipeline to provide a more interactive approach to the wavelength calibration, and provide additional tools to improve accuracy of the wavelength calibration for the O&E beam. Here we present a brief overview of the pipeline and the results for the blazars 3C 279, and 4C+01.02.

Speaker: Mr Justin Cooper (University of the Free State)

Cooper_FERMI22.pdf

10:35 Modelled light curve variability due to blob injection in RMHD jet simulations

Active Galactic Nuclei (AGN) are compact
and highly luminous regions at the centre of galaxies. Relativistic
jets from radio loud AGN have been shown to exhibit variability over
various time-scales and frequencies. A contributing component to the
formation of variability results from the injection and propagation of
blob/shock structures within the jet. We have investigated this
through three-dimensional RMHD simulations jets using PLUTO. A
constant jet was first allowed to develop in time forming multiple
re-collimation shocks, before a quasi-spherical blob was injected and
allowed to propagate along the jet, with blob-jet interactions
occurring along the propagation path. A post-processing code was used
to find the integrated specific intensity of the synchrotron emission
in the radio regime, accounting for Doppler boosting and
light-crossing time correction. Different types of blob injection were
tested, investigating the resulting light curves.

Speaker: Daniel Kulik (University of the Free State)

DM_Kulik_Fermi_2022_Poster.pdf

10:35 The first GeV flare of the radio-loud narrow-line Seyfert 1 galaxy PKS 2004–447

The extragalactic gamma-ray sky observed by Fermi-LAT is dominated by blazars, with only a handful of narrow-line Seyfert 1 (NLS1) galaxies detected in 10 years of observation. Flares from this elusive source class are among the rarest events that the Fermi-LAT has seen so far, and we are presenting the analysis on one such event from the radio- and gamma-ray loud source PKS 2004–447.
On 2019 October 25, PKS 2004–447 showed its first bright γ-ray flare since the beginning of the Fermi mission in August 2008. We obtained multi-wavelength follow-up observations with Swift, XMM-Newton, NuSTAR, and ATCA, and studied the variability across all energy bands, with a focus on short timescales in the γ-ray emission. We modelled the broadband spectral energy distribution (SED) data with a leptonic model during different activity states of the source.
The observations of PKS 2004–447, and γ-NLSy1 in general, point to a scenario in which these objects could be considered to belong to the blazar subclass of radio-loud emitters.

Speaker: Andrea Gokus (Dr. Karl Remeis-Observatory/ECAP)

Poster_PKS2004-447.pdf

10:36 Constraining magnetic fields and gamma-ray production zones in blazar jets by fitting the broad-band spectral energy distribution.

Active galaxies are complex astrophysical objects in that many physical processes occur almost simultaneously. They emit at all electromagnetic frequencies. Active galactic nuclei (AGNs) are the parent class of blazars which are the brightest of active galaxies. There are a number of models that can explain the spectral energy distribution (SED) of blazars. However, the complexity of blazars requires that these models have a relatively large number of parameters, such as the magnetic field in the jet environment, the location region of gamma-ray production, and the doppler factor of the bulk flow of particles in the jets, to name a few. To better understand these objects, work has to be done to place feasible constraints on all the parameters that play a role in the physical processes taking place in blazars. In this work, we place constraints on the gamma-ray production location and the magnetic fields in blazar jets. We place these constraints by doing a pilot case study on the well-studied bright blazar 3C 279. Using a broad-line region (BLR) model we developed in earlier work, we fit the broad-band SED of 3C 279. By accounting for this blazar's broad-line region, we show that the BLR can play an essential role in absorbing gamma-rays; this places some constraints on the location of these gamma-rays. Also, by filling the gamma-ray flux absorbed by the BLR, synchrotron self-Compton (SSC) emission from the electron-positron pairs produced in the BLR gives a way of constraining the magnetic field in blazars.

Speaker: Mr Mfuphi Ntshatsha (University of Johannesburg)

10:36 Gamma-ray emission from extended jets of LLAGNs - NGC315 and NGC4261

Despite occupying ∼40% of the local Universe, Low Luminosity Active Galactic Nuclei (LLAGNs) are less explored due to their faintness. Detection of a few in gamma rays by Fermi-LAT allows us to constrain the physical parameters of the jet by modeling their broadband spectral energy distributions. While a one-zone model explains the broadband emission up to a few GeV, another component is required to explain the excess beyond that. An extended jet for both NGC 315 and NGC 4261 has been seen in radio and X-rays. While the spectral index of X-ray emission implies a synchrotron origin, we find that the excess at GeV energies can be successfully explained by the inverse Compton scattering of the starlight from the host galaxy by the same electron population, in both cases. This observation suggests that electrons can be accelerated to ultrarelativistic energies at extended scales.

Speaker: Gunjan Tomar (Raman Research Institute)

Fermi-oct22-poster.pdf

10:37 A hadonic synchrotron mirror model for blazars - Application to 3C279

Blazars show variability across the electromagnetic spectrum on a variety of time scales. In some cases, flaring events in one frequency band are not accompanied by flaring in other bands. Such events are termed ”orphan flares”. The causes of this variability and conditions in and location of the high-energy emission region are not entirely understood. The hadronic synchrotron mirror model is suggested as a possible explanation for rapid orphan gamma-ray variability. We apply this model to a very-high-energy gamma-ray orphan flare of 3C279, which was observed by H.E.S.S. on the 28th of January 2018. A primary flare was observed 11 days earlier by Fermi-LAT. In our model, the Fermi-LAT spectrum is reproduced by proton synchrotron emission, which constrains the parameters of the ultra-relativistic proton population in the jet. A VHE orphan flare results from photo-pion interactions of this relativistic proton population with electron synchrotron radiation reflected back into the jet by a cloud acting as a mirror. We present both analytical estimates of the viability of the hadronic synchrotron mirror model and detailed numerical simulations. These demonstrate that a VHE orphan flare can be produced by this model, in accordance with observations, accompanied by only a very moderate Fermi-LAT flux enhancement. The photo-pion induced cascade component of the spectrum is in agreement with observations.

Speaker: Laenita Lorraine Oberholzer

poster_laenita.pdf

10:37 One-HaLe model for the SED of blazars and the curious case of CGRaBS J0211+1051

Blazars are a subclass of Active Galactic Nuclei (AGN) seen almost along the relativistic jet, which emanate from very close to the central super massive black hole. As these jets are close to our line of sight, blazars represent a unique sample to study the extreme particle energisation, nature of the magnetic field and many other physical properties of jets. Blazars are well known to show flux and spectral variations on diverse time scales.

The time dependent modeling of the spectral energy distribution (SED) and multi-frequency light curves is used to constrain many important physical parameters crucial to represent the steady state or outbursts; for example, the size and location of the emission region, particle spectra, acceleration mechanisms, magnetic field, etc. In many cases, the data collected over the years have changed our views about these enigmatic sources.

The recent data of CGRaBS J0211+1051 reveals a very interesting SED and the model constraints hint at a number of interesting facts about this particular blazar. The UV and X-ray parts of the SED do not connect smoothly suggesting hadronic contributions or contributions from another emission region. We shall be highlighting some of our recent findings from the lepto-hadronic modeling of the SED.

Speakers: Pranjupriya Goswami (North-West University), Dr Sunil Chandra (South African Astronomical Observatory, Cape Town)

Poster_Schandra.pdf

10:38 GRB 201216C: A TeV Detected Gamma-ray burst at z=1.1

Gamma-ray bursts are the most energetic cosmic explosions in the Universe, covering a spectral domain from all the way radio to gamma-ray up to tens of GeV. Recently, the detection of very high energy emissions (z ~ 0.0785 to 1.1) associated with the afterglows of a few GRBs by HESS and MAGIC telescopes has provided new insights into the research area of these fascinating objects. This work presents a multi-wavelength analysis of the prompt emission and afterglow of the most distant VHE detected GRB 201216C. We also compared our results with a sample of known VHE detected GRBs and found that most of the results obtained from GRB 201216C are similar to the VHE detected GRB 180720B.

Speakers: Mr Amit Kumar (Aryabhatta Research Institute of Observational Sciences), Amit Kumar (Aryabhatta Research Institute of Observational Sciences)

10:38 Neural Networks for Estimation of Gamma-Ray Burst Redshifts

A wealth of Gamma-Ray Burst (GRB) data is available today with known redshifts (observed up to z =9.4), provided by different instruments with well-measured prompt gamma-ray flux and spectral information. In order to estimate redshifts of GRBs using a theoretical estimate (so-called pseudo-redshifts) from spectral relations, several phenomenological relations have been developed. Amati relation between the peak energy E_i,_peak, in the cosmological rest frame of the GRB at which the νfν spectrum peaks and the total isotropic-equivalent radiated energy in gamma rays E_iso is one such example. Another example is the Yonetoku relations between the E_i,_peak, and isotopic luminosity L_iso. In this work, we adopt a machine learning technique (Neural Networks) to estimate redshifts from different observable GRB properties with a large sample of data collected by the Gamma-ray Burst Monitor (GBM) onboard the Fermi Gamma-ray Space Telescope. Such a technique is useful to explore any hidden, non-linear relations between the parameters. Estimation of pseudo redshift is useful to standardize GRBs as cosmological probes.

Speaker: Tamador Aldowma (Johannesburg University, Omdurman Islamic University)

10:39 Deep Search for and Investigations of Untriggered Gamma-Ray Transient Events Using Fermi/GBM Data

Gamma-Ray Burst Monitor (GBM) on board Fermi, designed to detect short transient events, has been continuously observing the entire sky in gamma-ray since its launch in 2008. Over the 14 years, GBM has produced the largest database of all-sky observations in gamma rays with high time resolution continuous data (2 µs; CTTE since July 2010). Such continuous data contain a wealth of relatively weaker short transient events that did not trigger the detectors. These short gamma-ray transient events can arise from several different astrophysical origins and scenarios such as GRBs, thermonuclear bursts from accreting neutron star systems, bursts from magnetars. Identification and investigation of untriggered events is crucial towards fully understanding the physical mechanisms responsible for the observed bursts. We searched for untriggered short gamma-ray transient events among the 11-year (2010-2021) GBM CTTE database. The search was done using three independent methods: 1. Signal-to-noise-ratio based, 2. Poisson statistics based, and 3. Bayesian statistics based. Each method has four different modes with different time and energy resolution, targeting different types of events. After the search, we first filtered out false event identifications caused by the spacecraft’s orbits (before and after the SAA passages) as well as known triggered events or Solar flares. The rest of the events found in the search were subsequently subjected to our classification algorithm. In this poster, we describe our search and classification methods and present the results that we obtained. The search results and the properties of the identified events will be publicly available on our comprehensive burst properties portal (http://magnetars.sabanciuniv.edu).

Speaker: Özge Keskin (Sabancı University)

fermi_poster_özge.pdf

10:40 The properties of the outflow and prompt emission of 14 LAT GRBs

The composition of the jet and the nature of the prompt non-thermal emission are open questions in gamma-ray bursts astrophysics. In this work, we study the degree of magnetisation of the jet and the prompt emission for 14 Fermi LAT GRBs with sub-dominant black-body components. We first carry out the joint spectral analysis of these GRBs with the GBM and LAT data using multi-component spectral models. We then use the results of the spectral analysis to study the characteristics of the jet and the prompt non-thermal emission in various scenarios.

Speaker: Saeeda Sajjad (Institute of Space Technology (IST), Islamabad Pakistan, Space and Astrophysics Research Lab (SARL), National Center for GIS and Space Applications (NCGSA), Islamabad, Pakistan)

poster_final.pdf

10:41 Modelling external inverse Compton emission of gamma-ray burst afterglows in the very-high-energy regime

Gamma-ray bursts (GRBs) comprise of short, bright, energetic flashes of emission from extragalactic sources followed by a longer afterglow phase of decreased brightness. Recent discoveries of GRB 180720B and GRB 190829A afterglow emission up to very-high-energy $\gamma$-rays by H.E.S.S. have raised questions regarding the emission mechanism responsible. We interpret these observed afterglows to be the result of inverse Compton (IC) emission of ultrarelativistic electrons in an external radiation field, and present predictions of spectra corrected for the $\gamma$-ray attenuation by absorption of photons through their interaction with the extragalactic background light (EBL). Thus, we fit an attenuated model of the form $dN/dE={(dN/dE)_{\rm EC}}e^{-\tau(E,z)}$, where $(dN/dE)_{\rm EC}$ is the intrinsic external Compton spectrum, the exponential term corresponding to the attenuation, and $\tau$ is the energy-dependent optical depth for a source at redshift $z$, to the data. Our model reproduces an increase in attenuation, due to the EBL, with source distance (above $z\approx 0.1$), whereas nearby GRBs experience less attenuation, requiring a smaller correction due to EBL absorption and allowing the intrinsic spectrum to be determined. These findings constrain the GRB environment assuming an IC emission mechanism which mitigates the particle energy requirements for the emission observed at late times and has consequences for the future observations of GRBs at these extreme energies.

Speaker: Dr Monica Barnard (University of Johannesburg)

10:41 The MAGIC VHE GRB program

Since the beginning of its operations, the MAGIC telescopes were optimised to perform fast observations of gamma-ray bursts (GRBs). The follow-up strategy and the specific design of these telescopes, namely a fast slewing system (7 deg/s), a low energy threshold (around 50 GeV) and the possibility of performing observations in not standard conditions (such as large zenith angle of observations and/or with moderate moonlight), let them to perform the first detections of GRBs in the very high energy (VHE, E>100 GeV) domain.These discoveries are shedding light on the physical processes at play in GRB sources. This contribution will highlight the current status of GRB studies with MAGIC, including the detection of GRB 190114C and GRB 201216C and the studies performed for the hint of detections from GRB 160821B and GRB 201015A.

Speaker: Francesco Longo

poster_FermiSymposium2022_full.pdf

10:42 Anisotropic diffusion cannot explain TeV halos

TeV halos have become a new class of astrophysical objects which were not predicted before their recent observation. They offer evidence that diffusion around sources (concretely, pulsars) is not compatible with the effective average diffusion that our models predict for the Galaxy. This directly impacts Galaxy formation, our knowledge of the propagation process throughout the Galaxy and our models of acceleration of charged particles by astrophysical sources like supernova remnants (SNRs) or Pulsar Wind Nebulae (PWN).
In this talk we show that, while anisotropic models may explain a unique source such as Geminga, the phase space of such solutions is very small and they are unable to simultaneously explain the size and approximate radial symmetry of the TeV halo population. Furthermore, we note that this conclusion holds for any CR-powered source (hadronic or leptonic), implying more generally that anisotropic diffusion does not dominate the propagation of particles near energetic sources (at least, below hundreds of TeV) because of the self-generated turbulence.

Speaker: Pedro De la Torre Luque

10:43 Particle acceleration in core-collapse supernova remnant expanding inside a wind bubble

Supernova Remnants (SNRs) are considered as the primary sources of galactic cosmic rays (CRs), where CRs are assumed to be accelerated by diffusive shock acceleration (DSA) mechanism, specifically at SNR shocks. In the core-collapse scenario, the SNR shocks expand
inside the complex ambient environment as the core-collapse SNRs have massive progenitor stars (> 8M⊙) and those stars generate wind-blown bubbles during their different evolutionary stages as a consequence of their mass-loss in the form of stellar wind. Additionally, as the evolution of massive stars depends on the Zero Age Main Sequence (ZAMS) mass, rotation, and metallicity the structures of created circumstellar medium are considerably different. Therefore, the CR acceleration and the radiation from the core-collapse SNRs should differ significantly not only from the SNR, evolving in the uniform environment but also from one
another, depending on their progenitor stars.

We aim to observe the influence of the ambient medium of core-collapse SNRs on the particle spectra and radiation as well as to probe the change in spectral shape if SNRs have progenitors with lower(> 8M⊙), intermediate, and very high ZAMS mass.

We applied the hydrodynamic structures of wind-blown bubbles at the pre-supernova stage created by massive stars with 20M⊙, 35M⊙, and 60M⊙ZAMS masses to form the ambient environment for supernova explosions. The evolution of those stars through notably different stages from Zero Age Main Sequence (ZAMS) to the pre-supernova stage results in the formation of structurally different wind bubbles, hence preferable to observe the spectral shape dependency on the mass of progenitor stars. Then, the transport equation for cosmic rays, hydrodynamic equations have been solved simultaneously in 1-D spherical symmetry.

We have obtained the modifications in particle spectra are significantly determined by the hydrodynamic structure of SNR ambient medium. The spectral shape depends considerably on the interplay of SNR shock interactions with different discontinuities inside the wind bubble and the temperature of the bubble. The 60M⊙star ends life as a Wolf-Rayet star and creates a very hot bubble (> 1e8 K). As consequence, we have found softer particle spectra with spectral index close to 2.5. For comparison, 20M⊙star becomes a Red-Supergiant at pre-supernova stage and hence the created bubble would not be hot enough to provide the spectral softness as
for the SNR with 60M⊙progenitor. Furthermore, the circumstellar magnetic field structure,as well as the considered particle diffusion coefficient in the simulation effectively influence the particle acceleration as well as emission morphology of SNRs.

Speaker: Robert B.

10:44 On the origin of the complex energy-dependent structure of HESS J1702-420

HESS J1702-420 is an unidentified multi-TeV gamma-ray source with a peculiar energy-dependent morphology which most naturally can be explained as a composition of two independent emission components with significantly different spatial and energy distributions. Here we propose an alternative interpretation assuming that we deal with a single hadronic accelerator injecting protons with energies extending to at least 0.5 PeV. In the suggested scenario, both the extended (elongated) component of radiation with a soft gamma-ray spectrum and the compact point-like component with a very hard spectrum have the same origin associated with the interactions of injected protons with the surrounding dense gas environment but are produced at different stages of proton propagation. The component produced at the initial (quasi) ballistic regime of proton propagation has a compact image (angular distribution) focused on the accelerator and an energy spectrum which reflects the acceleration spectrum. The second (extended) component is the result of radiation at the stage when the protons enter the diffusion stage of propagation. Thus the image of this component reflects the spatial distribution of protons. Its spectrum is steeper because of the modulation of the proton spectrum in the course of diffusion. The joint analysis of these two components allows us to derive the power-law index of the acceleration spectrum and the proton injection rate, and the energy-dependent diffusion coefficient. Assuming the distance to the source d=0.3 kpc, the characteristic medium density of ~100 cm$^{-3}$ and diffusion coefficient D(E)=3 x 10$^{26}$ cm$^2$/s we argue that the system can be well described by the protons' injection rate ~6 x 10$^{37}$ erg/s.

Speaker: Dr Masha Chernyakova (DCU)

2022_FERMI_HESSJ1702-420.pdf

10:45 Particle Acceleration at Reflected Shocks in Supernovae Remnants

Supernovae remnants (SNRs) are widely believed to be one of the prime sources of Galactic cosmic rays. They are known to be efficient particle accelerators which is indirectly confirmed by detection of non-thermal emission across the whole electromagnetic spectrum from radio to very-high-energy gamma-rays. Protons and electrons can be accelerated to very high energies of at least several tens of TeV both at the forward and at the reverse shock of the remnant. About 80% of all SNRs originate in core-collapse events and are expected to expand into a complex environment of the stellar wind bubble blown up by their progenitor stars, where forward shock might interact with various density inhomogeneities. Such interaction would cause the formation of reflected shocks propagating inside the remnant which can potentially be strong enough to also accelerate particles. Current investigations of particle acceleration in SNRs are usually limited to forward and reverse shocks ignoring the complexity of the hydrodynamic picture. Although for most SNRs the observed shell-like morphology generally agrees with an idea that high energy particles originate predominantly from the forward shock (for some remnants the significant contribution from the reverse shock was also confirmed), precise spatially resolved measurements do not always agree with a simplified picture giving rise to alternative ideas such as interaction with dense cloudlets . This work is focused on the investigation of particle acceleration at the reflected shocks formed through the interaction of the forward shock with density inhomogeneities and its potential impact on the overall observational properties.

Speaker: Mr Jacobus Frederik le Roux (North-West University)

FermiPoster.pptx-1.pdf

10:47 Searching the COMPTEL Data for Sources of the Fermi-LAT 1FLE Catalog

The first catalog of Fermi-LAT sources below 100 MeV (1FLE catalog, Principe et 2018) covers the energy range from 30 to 100 MeV. The catalog contains 198 sources of different nature, having a detection significance above 3 sigma. Most of these sources are of extragalactic nature with flat spectrum radio quasars (FSRQs) being the majority. The COMPTEL experiment aboard the Compton Gamma-Ray Observatory (CGRO) surveyed the sky for nine years (1991 to2000) at energies between 0.75 and 30 MeV, i.e. in the adjacent energy band on the lower side of the 1FLE catalog. The COMPTEL source catalog (Schönfelder et al. 2000) lists 32 steady sources, of which 14 have an association in the 1FLE catalog.
We have searched the COMPTEL data systematically for all 198 sources of the 1FLE-catalog for several periods in time windows as well energy bands. We found evidence on the 3-sigma level in the COMPTEL data for several of the 1FLE sources not yet associated to a COMPTEL source. We will report the results of these analyses by providing source lists and properties, present the combined COMPTEL and 1FLE spectra for interesting sources, and discuss the scientific implications.

Speaker: Dr Werner Collmar (Max-Planck-Institut für extraterrestrische Physik)

10:47 Simulating the Operations and Observations of BurstCube

Fermi’s observations of gamma-ray bursts (GRBs) allow us to model the next generation of GRB instruments, including CubeSats such as the soon-to-be launched BurstCube. Over the first 14 years of its operation, GBM has studied nearly 3500 GRBs, many in stunning detail, which is a significant sample for simulating aspects of BurstCube’s observations when combined with detailed simulations of the orbit and pointing profile. In this poster, we describe how we have used these observations of the prompt emission to seed a bootstrap analysis of BurstCube’s predicted on-orbit performance. During operation, BurstCube will primarily point zenith, scanning the entire unocculted sky for gamma-ray transients, with some deviations to minimize drag and maximize power to the solar panels. The four CsI scintillator detectors will take data continuously except for tracks through the South Atlantic Anomaly. Onboard triggers will be downlinked as quick binned data via TDRSS and automatically add the time-tagged event data to the next ground station pass. We will describe how this simulation predicts the on-orbit performance.

Speaker: Pi Nuessle (NASA Goddard Space Flight Center)

Nuessle_Pi_Brno_48x36.pdf

10:48 Progress of a future space Japanese mission for GRB observations: HiZ-GUNDAM

High-z Gamma-ray bursts UNraveling the Dark Ages and extreme space-time Mission (HiZ-GUNDAM) is a future astronomical space mission in the 2030s (a pre-project candidate of the competitively-chosen Middle-class ISAS missions) that performs wide-field X-ray surveys of X-ray transients such as gamma-ray bursts (GRBs) and follow-up observations in the infrared band.
By the observations in the infrared and X-ray bands, HiZ-GUNDAM can contribute to the multi-messenger astronomy, e.g., for clarifying origins of mysterious gravitational events and IceCube neutrino events. Also, it can detect very high-redshift GRBs (z > 7) to investigate unknown physical environments in the early universe.
In this presentation, we will introduce the mission status of HiZ-GUNDAM and development of the X-ray and infrared mission instruments.

Speaker: Makoto Arimoto

10:49 Synergies between SKA and LSST surveys

Next-generation radio surveys from the Square Kilometre Array (SKA) mid-frequency telescope and its precursors will observe the universe with high spectral precision. The 21-cm neutral hydrogen (HI) emission line detected from these surveys is ideal for obtaining more accurate constraints on cosmological parameters. However, the HI line is intrinsically faint and difficult to detect at high redshift. The Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST), forecast to observe the optical sky at large cosmic volumes with high spatial resolution, is a perfect candidate for complementing HI intensity mapping surveys. For this work, we present a new Bayesian framework for extracting redshift information by exploring the synergies between these major surveys. We update the methodology proposed by Harrison, Lochner and Brown (2017) to incorporate photometric redshift and spatial information from optical surveys such as LSST. We aim to determine the utility of such a technique in constraining the redshifts for distant type Ia supernova host galaxies in the LSST deep drilling fields and possibly providing a complementary training set for photometric redshift calibration.

Speaker: Nomthendeleko Motha

Motha_Fermi_Poster_2022.pdf

10:50 Next incremental release of the Fermi LAT source catalog

The latest Fermi-LAT source catalog (4FGL DR3: 6658 sources above 50 MeV) was based on twelve years (2008 - 2020) of data. Since neither the event reconstruction (Pass 8) nor the interstellar emission model (gll_iem_v07) has evolved since 2019, we provide incremental 4FGL releases at regular intervals of two years, until one of those two key ingredients changes. The next incremental catalog, 4FGL DR4 covering fourteen years of LAT data, will be released in 2023.
I will describe how we plan to improve the catalog for DR4 with respect to DR3, besides adding two years. Adding priors on the spectral curvature parameters helps to stabilize the source model at low energy. Smoothly modulating the diffuse model spatially avoids jumps between regions of interest. Leaving the spectral index of bright sources free in the light curves avoids residuals that can trigger false variability in faint nearby sources. Entering strongly variable sources that have average fluxes below detectability over the full time range ensures that their flare is not attributed to a neighbor.

Speaker: Jean Ballet

JBallet_4FGLDR4_v2.pdf

10:51 The LAT view on VHE sources

We present a catalog of LAT information on VHE sources. The purpose of the catalog is a compilation of complementary information from LAT and ground-based gamma-ray arrays on sources detected in the VHE energy band (E> 100 GeV)

Speaker: Prof. Stefan Wagner (LSW, ZAH, U Heidelberg)

10:52 Burst Properties of Two Magnetars: SGR J1818.0-1607 and PSR J1846.4-0258

Magnetars are isolated, young ($<10^5$ years), highly magnetic ($>10^{14}$ G) neutron stars with long spin periods (2-12 s). All magnetars emit short repeated bursts in soft gamma rays; however, only a handful of magnetars show radio pulsations. After the detection of magnetar-like bursts from highly magnetic ($>10^{13}$ G) Rotation Powered Pulsars (RPPs), the question of whether magnetar-like bursts from high-B RPPs have similar characteristics with other magnetars arose. To answer this question, we studied bursts from two magnetars, SGR J1818.0-1607 (a radio-loud magnetar) and PSR J1846.4-0258, both of which entered an active bursting episode in 2020, using Fermi Gamma-ray Burst Monitor (GBM) data. Fermi GBM triggered on December 13 in 2020, and January 6 & 24 in 2021 due to short bursts originating from SGR J1818.0-1607; and on August 1, 2020 due to a single burst coming from the direction of PSR J1846.4-0248. We searched for untriggered bursts and performed time-integrated spectral analysis for all identified bursts from both objects using three spectral models: Comptonized, black body, and sum of two black bodies with different $kT$ values. Here, we present the results of our comprehensive burst search, identification and spectral analyses for both sources, and discuss their characteristics with each other, as well as burst properties from other magnetars.

Speaker: mete uzuner (Sabancı University)

fermi_poster_mete.pdf

10:53 A Morphological Study and of the Light Curves of Gamma-ray Millisecond Pulsars

Millisecond pulsars are old recycled pulsars with a rotation period of less than 30 ms. The pulsed GeV emission mechanism of the MSPs is not fully understood. The Fermi LAT Third Pulsar Catalogue (3PC) will present light curves of unprecedented quality for more than 275 gamma-ray pulsars, with more than 100 of them being MSPs. As a part of our project, we are studying the morphology of the MSPs' light curves to perform the phase-resolved spectral analysis to probe particular prominent features (e.g., peaks, bridges, background emission). This model will be combined with a spectral model to represent the intensity as a 2-dimensional function of the phase and energy. In this poster, we present the first results of the phase-resolved spectral morphological analysis.

Speaker: Ms Hend Hamed (North-West University)

10:54 Radio pulsations from LS I 61 303

LS I +61 303 303 is one of the rare gamma-ray binaries, emitting most of their luminosity in photons with energies beyond 100 MeV. The ~26.5 d orbital period is clearly detected at many wavelengths. Additional aspects of its multi-frequency behavior make it the most interesting example of the class. The morphology of high-resolution radio images changes with orbital phase displaying a cometary tail pointing away from the high-mass star. LS I +61 303 303 also shows superorbital variability. A couple of energetic (~ 10^37 erg/s), short, magnetar-like bursts have been plausibly ascribed to it. LS I +61 303 303's phenomenology has been put under theoretical scrutiny for decades, but the lack of certainty regarding the nature of the compact object in the binary has prevented advancing our understanding of the source. Here, using observations done with the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we report on the existence of transient radio pulsations from the direction of LS I +61 303 303. We find a period P=269.15508 (\pm) 0.00016 ms at a significance of > 20 sigma. This is the first evidence for pulsations from this source at any frequency, and strongly argues for the existence of a rotating neutron star in LS I +61 303 303. We put this measurement in the context of models of the source, analyzing the possible state such pulsar could be in, and what kind of magnetospheric gamma-ray emission could be expect from it, if any.

Speaker: Diego F Torres

10:55 Modelling the observability of neutrinos from quiescent blazars with KM3NeT

After the detection of neutrinos from blazar TXS 0506+056 in a flaring state, there have been advancements in neutrino astronomy including a detection of neutrinos from a tidal disruption event. Blazar TXS 0506+056 and other neutrino sources were detected by the first-generation neutrino telescopes during transient states. The spectral energy distributions of blazars jet emissions can be explained by two types of models, leptonic and hadronic models, whether in a steady state or a transient state. In leptonic models, the high energy contribution is only from leptonic interactions while in hadronic models, the high energy contribution is mainly from hadronic interactions. Both types of models were consistent with blazar observations until the detection of TXS 0506+056 as a neutrino source confirmed that blazars are sites of hadron acceleration. In this study, we simulated blazar jet emission using OneHaLe - a tool for numerical modelling of AGN jet emissions with hadronic models - and to determine the detectability of neutrinos from steady state blazars with KM3NeT, a second-generation neutrino telescope which is currently under construction. We will be presenting the preliminary simulations of the event rates in KM3NeT during one year of observation with the detector in its future completed configuration.

Speaker: Bhuti Nkosi (University of the Witwatersrand, KM3NeT Group)

Poster_FERMI_final.pdf

10:56 The Fermi-LAT/GBM Mentoring Program (MP)

The Fermi-LAT/GBM Mentoring Program (MP) was formed in 2020. The primary goal of the MP is to establish an effective mentoring structure, which provides a resource for graduate students to form strong and lasting relationships with their mentors, communicate any questions they have, discuss any issues that arise, help the student feel well-integrated within the Fermi-LAT/GBM Collaborations, and, ultimately, help identify and remove barriers to success. To this end, the program identifies suitable mentors for each interested student and the provision of resources, including training, to both mentors and mentees to facilitate the establishment of a productive relationship. After [three] cycles of the MP, we here present the structure of the program, lessons learned, and the plans for the upcoming cycles.

Speaker: Giovanna Senatore

FS2022_FermiMPposter.pdf

10:57 Exotic dark matter searches in dwarf spheroidal galaxies with the MAGIC telescopes: From secluded and branon DM to probing DM annihilation into neutrinos

One of the most pressing questions for modern physics is the nature of dark matter (DM). Several efforts have been made to model this elusive kind of matter, whose presence has been assessed only by gravitational effects so far. The largest fraction of DM cannot be made of any of the known particles of the Standard Model (SM). The ground-based gamma-ray telescope system MAGIC could potentially detect DM indirectly, by observing secondary products of either its annihilation into SM particles or its annihilation into short-lived mediators decaying into SM particles. We present a collection of exotic DM searches in dwarf spheroidal galaxies (dSphs) with the MAGIC telescopes. At first, we focus on brane-world theory as a prospective framework for DM candidates beyond the SM of particle physics. Secondly, we explore secluded DM by introducing short-lived mediators in the annihilation process. Last, we probe the DM annihilation into neutrinos, which produce a non-negligible fraction of gamma-rays and charged leptons in the final state. We present the cross-section limits as a function of the DM particle mass obtained by using a joint binned likelihood analysis, with the inclusion of systematic uncertainties in the residual background intensity and statistical uncertainties in the DM content of the dSphs.

Speaker: Tjark Miener (IPARCOS, UCM)

ExoticDM_10Fermi_TjarkMiener.pdf

10:58 Properties of Coronal Mass Ejection and Type II Solar Radio Burst Associated with Sustained >100 MeV Gamma-ray Emission Event Observed by FERMI/LAT

Sustained gamma-ray emission (SGRE) events observed by FERMI/LAT at >100 MeV energies are associated with fast and wide coronal mass ejections (CMEs) from the Sun. These CMEs are similar to those that cause ground level enhancement in solar energetic particle (SEP) events. CME-driven shocks have been suggested to be the acceleration site of the >300 MeV protons producing the >100 MeV gamma-ray emissions. Correlation between the durations of SGRE events and type II solar radio bursts that are produced by shock-accelerated electrons support the idea. We discuss the CME and type II radio burst properties associated with the SGRE event observed on 7 June 2011. The near-Sun peak speed of the CME was 1680 km/s and it accelerated relatively fast. It produced an SEP event with a fluence spectral index of 2.22$\pm$0.22 and it was associated with a GOES M2.5 X-ray flare. At the end time of type II radio burst, the shock had traveled to a radial distance of 75.5 R$_{\rm{sun}}$ and had a speed of about 1000 km/s. The estimated durations of the SGRE and type II radio burst were 3.08$\pm$1.67 hr and 10.93$\pm$0.32 hr, respectively. We discuss briefly also the limitations the gamma-ray, CME and radio observations.

Speaker: Pertti Makela (The Catholic University of America, Washington DC, USA and NASA Goddard Space Flight Center, Greenbelt MD, USA)

PerttiMakela_poster_FermiSymposium2022_A0.pdf

10:59 Multi-messenger Astrophysics Master Class: Gamma Rays

As part of the international gravitational wave collaboration for education and public outreach (IGRAV), Fermi communications and outreach is supporting the development of the gamma-ray content for a Multi-Messenger Astrophysics Master Class. The Master Class is being created for use in high schools, and represents how scientists work together using different types of data to make sense out of astrophysical phenomena. The event that inspired the class is GRB170817A (GW170817), the “golden binary” neutron star merger observed by more than 70 ground and space-based instruments on August 17, 2017. Along with the gamma-ray activities that use Fermi GBM data, activities are being developed by IGRAV members for other messengers including: gravitational waves, x-ray and radio data, and visible light data. The students will be divided into teams: each team will study one type of messenger for the first two days. On the final day, all the data will be combined to reveal the big picture, and to measure the Hubble constant.

The first day’s activities introduce the messenger and physical information about the types of events that will be analyzed. For Fermi, this is the “gamma-ray burst game” in which the students are asked to sort 15 different bursts into categories based on properties. This game is complete and can be played at the Astronomy from Home website (http://afh.sonoma.edu, see the Discover tab). Day 2 combines information as teams pass results from day 1 to other teams, and continues the analysis of the candidate event. For the gamma-ray messenger team, this means analyzing three different bursts to determine T90, and then classifying the candidate burst. Using additional positional information from the other teams, the gamma-ray team will then add in the GBM data to determine an approximate sky location for the event. Finally, the observed luminosity will be compared to a model of the flux expected at the measured distance, and the inclination angle to the jet axis will be determined.

This research was supported by NASA grant #80NSSC22K0081 to Sonoma State University. We greatly appreciate the work done by Jesse Nelson, Adam Kinmont, and Casey Lewiston in support of the gamma-ray burst game.

Speaker: Lynn Cominsky

FsymPostIGrav090822pm.pdf

11:00 → 13:00 Plenary 4: AGN

Convener: benoit Lott (LPI2B)

11:00 Multi-wavelength emission of blazars: connecting theories with observations

Blazars are the most numerous extragalactic gamma-ray sources seen by Fermi. While their multi-wavelength emission is often considered as leptonic, recent detection of a very high energy neutrino event by IceCube in coincidence with a Fermi gamma-ray flare of the blazar TXS 0506+056 suggested a potential hadronic origin. This talk reviews the recent progress in multi-wavelength studies of blazars, focusing on connecting theories with observations. In the past decade, numerical simulations of the blazar jet, including magnetohydrodynamics, Fokker-Planck treatment of particle evolution, particle-in-cell simulations, have revealed the dynamical evolution of the jet plasma and particles based on solid physics. Comprehensive radiation transfer simulations have enabled the direct comparison of these numerical results with multi-wavelength blazar observations, yielding important new insights into the jet physics. This approach will continue to serve as a powerful tool in the multi-messenger era of blazar studies.

Speaker: Dr Haocheng Zhang (NPP Fellow/NASA GSFC)

FermiSymposium.pdf

11:30 High-energy neutrino sources and their electromagnetic counterparts in the Fermi-LAT era

A new era for multi-messenger astronomy has begun with the detection of the flaring gamma-ray blazar TXS 0506+056 in spatial and temporal coincidence with the high-energy neutrino IC-170922A. Since this outstanding result, several associations have been proposed between high-energy neutrinos and cosmic accelerators observed at different wavelengths. The Fermi-Large Area Telescope (LAT), which has continuously monitored the gamma-ray sky for more than 14 years, plays a key role in the identification of candidate neutrino sources. It provides crucial input to population studies, as well as realtime observations of exceptional transient events coincident with single high-energy neutrinos.
In this contribution, I will present an overview of the main results obtained in the identification of candidate counterparts to high-energy neutrinos, focusing on the crucial contributions of Fermi-LAT observations to the multi-wavelength synergies in the astronomical community. I will also discuss future prospects and strategies in the multi-wavelength searches for counterparts to astrophysical neutrinos.

Speaker: Simone Garrappa

NeutrinoSources_SGarrappa_FermiSymposium2022_Final.pdf

12:00 Physics of neutrino emission from blazars

The number of potential associations of very-high-energy neutrino alerts with flaring blazars is steadily increasing, leading to an emerging picture that blazars are a likely source of at least some of the IceCube-detected VHE neutrinos. In this talk, I will discuss the general physics requirements for neutrino production in blazar jets as well as recent modeling results of individual candidate neutrino-emitting blazars, beyond the well-known case of TXS 0506+056.

Speaker: Markus Boettcher

Boettcher_Fermi2022_template.pdf

Boettcher_Fermi2022_template.pdf

Boettcher_Fermi2022_template.pptx

12:15 Bridging the Gap - The first sensitive 20-200 MeV catalog

The under-explored MeV band has an extremely rich scientific potential. Awaiting an all-sky MeV mission, it is now the prime time to take full advantage of the capabilities of the Fermi Large Area Telescope to explore this regime. With more than 12 years of the best available dataset (Pass8), we have developed an all-sky analysis to build a sensitive catalog of sources from 20 to 200 MeV. This work will allow us to cover the SED peak of many gamma-ray sources, fundamental to understanding their nature, and possibly discover a whole new population of MeV ones. Importantly, this program will start bridging the gap between the MeV and GeV energy bands, strongly supporting the scientific case for future all-sky MeV missions and enhancing the legacy of the Fermi mission. In this talk I will present the preliminary results of this analysis, highlighting the scientific potential of this project. I will also discuss the difference with respect to the first catalog of low-energy sources (1FLE, Principe et al. 2018).

Speaker: Lea Marcotulli (Yale University)

10th Fermi Symposium .pdf

12:30 A multi-wavelength spectral characterization of extreme BL Lacertae blazar candidates hidden in the 4FGL catalog.

Blazars are jetted radio-loud active galactic nuclei of particular interest in astroparticle physics. Their non-thermal emission, which extends from radio to gamma rays, dominates their broadband spectrum and it is proof of cosmic particle acceleration and production of ultra-relativistic particles. Of particular importance in gamma-ray astronomy are the extreme high-synchrotron-peak (EHSP) BL Lac objects. This subclass is mainly characterized by inefficient accretion and radiation processes, and a high-energy emission which is expected to peak at TeV energies. However, only a rather limited number of these sources are known. In this talk, we show a novel methodology for their identification based on observations from NASA’s Fermi Gamma-ray Space Telescope plus archival radio, optical, and X-ray data. This strategy allows a systematic study of their physical properties. Our main results are (1) finding 17 new EHSP blazars, increasing significantly their number; (2) that only 2 of them are expected to be detectable with Cherenkov telescopes, including the Cherenkov Telescope Array, in contrast with the general belief that these sources are efficient TeV emitters; and (3) interestingly, these 2 objects are outliers relative to their magnetic versus kinetic energy density. We discuss the interpretation of these results.

Speaker: Mireia Nievas

Extreme_EHSP_FermiHidden_FermiSymposium2022_withtemplate.pdf

12:45 Multi-wavelength Study of Radio Galaxies in MeerKAT fields

Radio galaxies are galaxies with an active nucleus (AGN = active galactic nucleus), harboring a super-massive black hole, powering relativistic beams (jets) of particles that extend over thousands of light years into intergalactic space (see, e.g., Boettcher, Harris & Krawczynski, 2012, for an introductory text book). While bright radio emission produced in the jets and their termination regions is the defining signature of radio galaxies, the jets are known to emit across the electromagnetic spectrum, including X-rays and gamma-rays, with a handful of them even detected at very-high-energy (VHE, > 100 GeV) gamma-rays by ground-based atmospheric Cherenkov Telescopes (e.g., Cen A: H.ES.S. Collaboration 2009, 2018; M87: VERITAS Collaboration 2008, 2012). A comprehensive multi-wavelength approach is therefore necessary to understand the physics of these jets and their interaction with the intergalactic medium.

Most gamma-ray detected AGN belong to the sub-class of blazars, in which one of the jets points close to the line of sight towards Earth, leading to relativistic Doppler boosting. In such a configuration, it is usually impossible to spatially resolve the inner jet region to identify the dominant site(s) of particle acceleration. Radio galaxies, on the other hand, offer a side-on view of the jet, where a spatially resolved study is much more feasible. The proposed project therefore aims at identifying well resolved radio galaxy jets in MeerKAT images and probing spatially resolved multi-wavelength spectral features.

MeerKAT has observed a number of fields in some PI projects, and with the field of view of 2.7 deg2 corresponding to about 9 full moons arranged in a 3 x 3 grid, a large number of sources (outside the primary targets of the PIs), including many radio galaxies, are covered. Among these sources are radio galaxies showing interesting morphologies. With the ultra-high sensitivity of MeerKAT, new detections of faint radio galaxies abound in these fields.

The aim will be to (a) identify potentially interesting objects within the available MeerKAT fields for further study, based primarily on their radio morphology; (b) assemble available archival multi-wavelength data, including infrared, optical, and X-ray surveys as well as data from the Fermi Gamma-Ray Space Telescope; (c) build multi-wavelengths spectral energy distributions for those sources for which sufficient multi-wavelength coverage exists; and (d) interpret them in the framework of AGN jet emission models to diagnose the physical properties of the jets and their environments.

Speaker: Dakalo Phuravhathu (North Weat University)

Fermi_Symposium_Phuravhathu DG.pdf

13:00 → 14:00 Lunch

14:00 → 15:30 Parallel 3: AGN I

Convener: Hartmut Winkler (University of Johannesburg)

14:00 Recent VERITAS Blazar Highlights

VERITAS (the Very Energetic Radiation Imaging Telescope Array System) is an array of four 12-meter imaging atmospheric Cherenkov telescopes located at Fred Lawrence Whipple Observatory in Arizona. VERITAS is sensitive to gamma rays with energies between 85 GeV to 30 TeV. First light for the four telescope array was in 2007, shortly before the launch of Fermi. VERITAS has a large extragalactic program that includes hundreds of hours of blazar and radiogalaxy observations each year. Recent blazar results will be presented, including: discovery of very high-energy gamma-ray emission from the extreme BL Lac RBS 1366, flaring activity from several blazars (e.g. Mkn 421, 3C 279, PKS 1222+216, Ton 599, VER J0521+211, H 1426+428), and the results of an unbiased survey of high-frequency-peaked BL Lacs. Emphasis will be placed on results involving both VERITAS and Fermi data.

Speaker: Megan Splettstoesser

SplettstoesserMeganFermiSymposiumVERITASBlazarHighlights.pdf

14:15 Studying the multi-wavelength properties of gamma-ray flaring blazars at redshift > 3

High-redshift (z > 3) gamma-ray blazars offer the possibility to study black hole growth, accretion processes and jet acceleration in the early Universe. The most luminous blazars, detectable out to high redshifts, tend to have the peaks in their non-thermal spectral energy distributions (SEDs) at relatively low frequencies, with the high-energy peak often appearing at MeV energies. In addition, the cosmological redshift further shifts the SED peaks towards lower frequencies.
Because of their low fluxes and soft gamma-ray spectra, the detection of gamma-ray emission from these sources is difficult and only about a dozen have been detected by the Large Area Telescope (LAT) onboard the Fermi satellite.
Flaring events provide a unique opportunity to detect and characterize the gamma-ray emission from high-z blazars and to gather contemporaneous multi-wavelength observations that are necessary to interpret their broadband SED.
For this reason, we have designed a program to find flares in high-z blazars by using the public Fermi/LAT data, which is well-suited to triggering multi-wavelength observations.
In February 2022, we detected a flare from the very distant blazar GB 1508+5714 (z=4.31), whose detection at gamma-ray energies was reported in 2017. The flux increase was accompanied by a significant hardening of the gamma-ray spectrum. We obtained follow-up observations across the electromagnetic spectrum, with special focus on observations at radio frequencies. We launched a dense, long-term monitoring campaign with the Effelsberg radio telescope to study the radio-gamma correlation for the blazar. Previous VLBI observations revealed an extended jet emission from GB 1508+5714. Hence, we acquired three VLBI observations with the VLBA that are taken within eight months in order to search for potential changes in the appearance of the jet.

Speaker: Andrea Gokus (Dr. Karl Remeis-Observatory/ECAP)

Gokus_high-z_blazar_detection_with_LAT.pdf

14:30 Southern African Large Telescope Spectroscopy of Fermi-LAT Blazars

More than 250 galactic and extragalactic very-high energy gamma-ray sources have been detected to date with imaging atmospheric Cherenkov telescopes. At present, Active Galactic Nuclei (AGNs) make up about 35% of such sources, the majority of which are blazars, i.e. their jets are closely aligned with the line of sight to Earth. At lower energies, blazars also dominate the population of gamma-ray sources in the Fermi-LAT observations and catalogs. Three quarters of blazars are classified as the high-frequency peaked BL Lacertae objects (BL Lacs). One of the challenges to studies of the cosmological evolution of BL Lacs is the difficulty of obtaining redshifts from their nearly featureless, continuum-dominated spectra. It is expected that a significant fraction of the AGNs to be detected with the future world-wide Cherenkov Telescope Array (CTA) Observatory will have no spectroscopic redshifts, compromising the reliability of indirect studies of the extragalactic background light density and direct studies of BL Lac populations, particularly of their cosmic evolution. Driven by such concerns, a spectroscopic observing program was started under the CTA redshift determination group in 2019, involving the use of some of the world’s most sensitive telescopes, including the Southern African Large Telescope (SALT), to measure the redshifts of a large fraction of blazars that are likely to be detected with CTA. The sample of objects that have been observed to date under the program was selected using the Fermi 3FHL catalog. In this contribution, I will present some results of the program, specifically those obtained from observations with SALT, the on-going collaborative efforts and plans for the future.

Speaker: Eli Kasai (University of Namibia)

KASAI_SALTSpecroscopyFermiLATBlazars2022_final.pdf

14:45 The variety of extreme blazars in the AstroSat view

We present a spectral study of extreme blazars (also eHBL) which are
known to exhibit hard intrinsic X-ray/TeV spectra and extreme SED peak
energies. We study four eHBLs 1ES 0120+340, RGB J0710+591, 1ES 1101-
232, 1ES 1741+196 and one HBL 1ES 2322-409 using new X-ray data from
AstroSat, together with quasi-simultaneous Fermi-LAT and other archival
multi-frequency data. Three of the eHBLs are non-variable, as is typically attributed. On the contrary, RGB J0710+591 shows spectral softening in both X-ray and GeV bands indicating a significant change in the synchrotron cut-off. Typically, a standard one-zone synchrotron self-Compton (SSC) model reproduces well eHBL SEDs, but often requires a large value of the Doppler factor and minimum electron energy. We have thus conducted a detailed investigation of the broadband SEDs under both leptonic and (lepto-)hadronic scenarios. We employ 1) a steady-state one-zone synchrotron-self-Compton (SSC) code and 2) a one-zone hadro-leptonic (OneHaLe) code. The latter is solved for two cases of the high energy emission – a pure hadronic case (proton synchrotron) and a lepto-hadronic case (synchrotron emission of secondary electrons from pion decay and Bethe-Heitler pair production). We find that all models can reproduce the
SEDs of eHBLs. For the normal HBL, SSC and proton synchrotron models
are superior to the lepto-hadronic model.

Speaker: Pranjupriya Goswami (North-West University)

PGoswami_Fermi_symp2022.pdf

15:00 Modeling the Multi-wavelength Polarization and Spectral Energy Distributions of Blazars

In the radio through optical-UV/X-ray regime, blazars emit highly polarized (nonthermal) synchrotron emission. Emission from the dusty torus, broad line region, accretion disk and host galaxy is of thermal origin and unpolarized. In some cases, their contribution is visible in spectropolarimetry wherein the unpolarized thermal emission dilutes the synchrotron polarization. However, partially ordered magnetic fields decreasing with distance along the jet from a shock also yield a decrease of polarization towards longer wavelengths in some sources. The Large Science Program ``Observing the Transient Universe" using the Southern African Large Telescope provides target-of-opportunity spectropolarimetry observations of $\gamma$-ray bright blazars, indicating a decrease in the total degree of polarization towards shorter or longer wavelengths in many sources. The program includes co-ordinated multi-wavelength observations from the Las Cumbres Observatory, the Swift-XRT and the Fermi-LAT. A shock acceleration model including the effects of magnetic-field compression and gradual restoration of the original magnetic-field configuration behind the shock is implemented to study the multi-wavelength spectral energy distributions and spectropolarimetry of blazars observed in steady states. In this presentation, the model is discussed in application to 3C 273, 3C 279 and 4C+01.02. Spectropolarimetry contributes to our understanding of the high-energy polarization, most notably the IXPE observations of 3C 273 and 3C 279.

Speaker: Hester Schutte

Fermi22Schutte.pdf

15:15 Effects of non-continuous losses during inverse Compton cooling in blazars

Blazar flares are ideally suited to study the extreme physics of relativistic outflows, with the primary method for this objective being physical modeling of the varying broad-band emission from blazar jets. Many of the numerical codes developed for this task, are based on the kinetic approach tracking the particle spectrum evolution due to various physical processes (acceleration, cooling, etc). In the existing leptonic codes, the inverse Compton (IC) cooling of electrons is described with a continuous-loss term in the kinetic equation, which is however only valid when the relative losses are much smaller than unity. In the Klein-Nishina (KN) regime, this is no longer the case, and one has to treat properly the large relative jumps of electrons in energy. The full transport equation then becomes an integro-differential one, and is quite challenging to solve. To avoid this issue, continuous-loss approximations attempting to include KN effects were derived by different authors. Here, we explore the limits of applicability of such approximations for typical conditions during blazar flares. To solve the kinetic equation with the full cooling term, we extend our blazar flare modeling code EMBLEM, and using it, investigate the importance of the non-continuous cooling effect on the electron spectrum and spectral energy distribution (SED). Finally, we explore the parameter space and identify the range of physical conditions in which these effects manifest the most.

Speaker: Anton Dmytriiev (North-West University)

Fermi_Symposium_2022_Dmytriiev_cooling.pdf

14:00 → 15:30 Parallel 4: Binaries

Convener: David Buckley (South African Astronomical Observatory)

14:00 Observation of the gamma-ray binary HESS J0632+057 with the H.E.S.S., MAGIC and VERITAS telescopes

The gamma-ray binary HESS J0632+057 has been observed at very-high energies (E>100 GeV) for more than ten years by the major systems of imaging atmospheric Cherenkov telescopes H.E.S.S., MAGIC, and VERITAS together with observations at X-ray energies and measurements of the Halpha emission line. We present a summary of the results including correlation studies between different energy bands and the updated gamma-ray light curve covering now all phases of the orbital period with significant detections in almost all orbital phases. This wealth of new data is interpreted taking into account the insufficient knowledge of the ephemeris of the system, and discussed in the context of results reported on other gamma-ray binary systems.

Speaker: Daniela Hadasch

DHadasch_HESSJ0632_FermiSymp2022.pdf

14:15 The unexpected multiwavelength behaviour of PSR B1259-63 during 2021 periastron passage.

PSR B1259-63 is a gamma-ray binary system hosting a radio pulsar orbiting around a massive young star, LS 2883, with a period of ∼3.4 years. The interaction of the pulsar wind with the LS 2883 outflow leads to unpulsed broadband emission in the radio, X-ray, GeV, and TeV domains. One of the most unusual features of the system is an outburst of GeV energies around the periastron, during which the energy release substantially exceeds the spin down luminosity under the assumption of the isotropic emission. Our recent intensive multi-wavelength campaign (radio, optical, X-ray and GeV bands) covered a period of more than 100 days around the 2021 periastron and revealed substantial differences from previously observed passages. In particular, these observations demonstrated substantial delay of the peak of the GeV flare and its relative weakness on short (~15 minutes) time scale. In addition to this we observed, for the first time, the presence of a 3rd peak in the X-ray lightcurve during which the previously observed correlation with the radio band disappears. In this talk I will discuss these and other features of the 2021 periastron passage and compare the obtained data set with the predictions of the emission cone model.

Speaker: Dr Masha Chernyakova (DCU)

psrb_10thFSymp_2022.pdf

14:30 Physical implications of gamma-ray emission from Cyg X-3

Cyg X-3 is unique among accreting X-ray binaries in being a powerful source of gamma rays. Also, its gamma-ray emission, associated with major radio flares, takes place mostly in the soft spectral state. This is different from other accreting binaries, in which the radio emission is strongly quenched in the soft state. Detailed analysis of the gamma-ray, radio and X-ray emission from Cyg X-3 until early 2017 was given in Zdziarski et al. 2018, and a physical interpretation of these results in terms of magnetically driven disc outflows was given by Cao & Zdziarski 2020. Since 2017, Cyg X-3 has shown gamma-ray flaring much stronger than that observed earlier. We present an analysis of these new data, allowing us to update the physical interpretation of the emission.

Speaker: Andrzej Zdziarski

CygX3_Fermi22.pdf

14:45 Gamma-gamma absorption in gamma-ray binaries

Gamma-ray binaries are a rare class of high mass binary systems that show persistent gamma-ray emission. The systems consist of an O or B/Be stars in orbit with a compact object in the mass range of a neutron star or black hole. The compact object for the majority of these systems is most likely a non-accreting pulsar, and the non-thermal emission originates from the shock that forms between the pulsar and stellar winds. However, very high energy gamma-rays produced near the apex of the shock should be subject to high optical depths, due to gamma-gamma absorption with the stellar photon field. A second shock cause by the orbital motion of the system, as found in RMHD simulations, has been suggested as a second location for the production of the very high energy emission. We present results of the expected gamma-gamma absorption for most known gamma-ray binaries, and discuss how this could modify the observed gamma-ray spectrum, and whether this may provide constraints on where the very high energy emission originates from.

Speaker: Brian van Soelen

gammagamma_fermi_2022.pdf

15:00 Analysing the orbital solutions of the gamma-ray binary HESS J0632+057 with new radial velocity measurements from SALT

Gamma-ray binaries are a small subclass of high mass binaries, consisting of O or B/Be type stars and a compact object (in the mass range of a neutron star or black hole), that produce multiwavelength non-thermal emission up to TeV energies. The gamma-ray binary HESS J0632+057 still has no clear orbital solution, required to correctly interpret how the non-thermal emission is produced by the system. Two different, and incompatible solutions were proposed by Casares et al. 2012 and Moritani et al. 2018, through radial velocity measurements of the absorption lines and the Hα emission line respectively. In order to better constrain the orbital solution we are undertaking independent radial velocity measurements, consisting of both the photospheric absorption lines and the Hα, Hβ and Hγ emission lines, using the optical spectra obtained with the HRS on SALT. In addition, we have investigated the archival data from the Moritani et al. and the Casares et al. studies, in order to analyse the effect of the updated orbital period of 316.8 and 317.3 days, determined from the modulated X-ray and TeV emission respectively, on the orbital solutions. We present the initial results from this campaign.

Speaker: Ms Natalie Matchett (University of the Free State)

Natalie_Matchett_Fermi2022.pdf

15:15 Shaken, not stirred: test particles in binary black hole mergers.

In light of the recent detections of multiple gravitational-wave events, originating from both neutron-star and binary-black-hole mergers, we simulate the dynamics of ambient test particles in the gravitational potential well of a BBH system close to its inspiral phase with the goal of simulating the associated electromagnetic radiation and resulting spectral energy density distribution of such a BBH system. This could shed light on possible detection ranges of electromagnetic counterparts to BBH mergers. The potentials are numerically calculated using embedded adaptive time step Runge Kutta methods, under the assumption of non-rotating black holes with the post-Newtonian Paczynski-Wiita potential approximation in tandem with retarded time concepts analogous to electrodynamics. We find that the frequencies of potential electromagnetic radiation produced by these systems drop off at 10^6Hz.

Speaker: Pieter Van der Merwe

Pieter_vd_Merwe_Fermi_2022.pdf

Pieter_vd_Merwe_Fermi_2022.pptx

15:30 → 16:00 Coffee Break

Posters

16:00 → 17:30 Parallel 5: AGN II

Convener: Marcos Santander (University of Alabama)

16:00 Modeling TXS 0506+056 for AMEGO-X

TXS 0506+056 is the first multimessenger blazar. We develop a one-zone, leptohadronic particle transport model and examine the multiwavelength SED simultaneous with each neutrino event. The model is specifically designed to examine the effects of particle acceleration on the observable data through self-consistent implementation of both acceleration and emission processes. We also compare with simulations of AMEGO-X data that suggest it is well poised to differentiate between physical models of multimessenger blazar flares.

Speaker: Tiffany Lewis

FermiSymp_Lewis.pdf

FermiSymp_Lewis.pptx

16:15 Searches for neutrino point sources with IceCube

The discovery of a diffuse flux of astrophysical neutrinos opens up pressing questions about the nature of the astronomical objects producing it. The quest for the sources of the diffuse, high-energy neutrino signal led to the identification of the first compelling candidate, the blazar TXS 0506+056. Furthermore, the survey on 10 years of IceCube data revealed an excess at the 2.9$\sigma$ level from the direction of the nearby Seyfert 2 galaxy NGC 1068. Despite these intriguing observations, the vast majority of the discovered high-energy neutrinos remain unresolved. In this contribution, we report on the most recent results from the search for neutrino point sources.

Speaker: Chiara Bellenghi (Technical University Munich)

Fermi_Symposium_Bellenghi.pdf

16:30 Modeling multiwavelength emission from the blazar TXS 0506+056

The MAGIC collaboration has recently analyzed data from a long-term multiwavelength campaign of the $\gamma$-ray blazar TXS 0506+056. In December 2018, it was flaring in the very-high-energy (VHE; $E>100$ GeV) $\gamma$-ray band, but no simultaneous neutrino event was detected. We explore prospects for detecting $\gamma$-rays and neutrinos of hadronic origin, produced both inside and outside the jet of TXS 0506+056, while coherently modeling the observed spectral energy distribution (SED) and neutrino flux upper limits. We constrain the neutrino flux through the restriction from observed X-ray flux on the secondary radiation due to hadronic cascade. We propagate the escaping ultra-high-energy cosmic rays (UHECRs; $E\ge 0.1$ EeV) in a random, turbulent extragalactic magnetic field (EGMF). The leptonic emission from the jet dominates the GeV range, whereas the cascade emission from CR interactions in the jet contributes substantially to the X-ray and VHE range. The line-of-sight cosmogenic $\gamma$ rays from UHECRs produce a hardening in the VHE range of the SED. Neutrino signal from the jet showed little or no variability during the MAGIC campaign. Therefore, we infer that the correlation between VHE $\gamma$ rays and neutrino flare is minimal. The luminosity in CRs limits the cosmogenic $\gamma$-ray flux, which, in turn, bounds the RMS value of the EGMF to $\ge 10^{-5}$ nG. The cosmogenic neutrino flux is lower than the IceCube-Gen2 detection potential for 10 yrs of observation. VHE $\gamma$-ray variability should arise from an increased activity inside the jet. Upcoming $\gamma$-ray imaging telescopes, such as the CTA, will be able to constrain the cosmogenic $\gamma$-ray component in the SED of TXS 0506+056. Detecting a steady flux at multi-TeV energies will validate blazars as unambiguous sources of UHECRs.

Speaker: Dr Saikat Das (Center for Gravitational Physics, Yukawa Institute for Theoretical Physics, Kyoto University)

saikat_111022.pdf

16:45 Blazars beyond the "Blob"

We apply the detailed black hole magnetosphere models of Nathanail & Contopoulos to model the polarization properties and neutrino emission from blazars. We show that the polarized emission properties (evolution of PA, correlation between degree of Polarization and flux is similar to that of pulsars, indicating a similar underlying geometry. The additional difference in blazars from pulsars is that the corresponding magnetospheres can also include protons (from the accretion disk) in magnetospheric regions of positive charge density. We show that these protons can then produce the observed neutrinos detected by Ice Cube.

Speaker: Demosthenes Kazanas (NASA/GSFC)

17:00 ExHaLe-jet: Modeling blazar jets with an extended hadro-leptonic radiation code

Blazars emit across all electromagnetic wavelengths. While the so-called one-zone model has described well both quiescent and flaring states, it cannot explain the radio emission and fails in more complex data sets, such as AP Librae. In order to self-consistently describe the entire electromagnetic spectrum emitted by the jet, extended radiation models are necessary. Notably, kinetic descriptions of extended jets can provide the temporal and spatial evolution of the particle species and the full electromagnetic output. Here, we present the initial results of a newly developed hadro-leptonic extended-jet code: ExHaLe-jet. As protons take much longer than electrons to lose their energy, they can transport energy over much larger distances than electrons and are therefore essential for the energy transport in the jet. Furthermore, protons induce injection of additional pairs through pion and Bethe-Heitler pair production, which can explain a dominant leptonic radiation signal while still producing neutrinos. In this talk, we discuss the differences between leptonic and hadronic dominated SED solutions, the SED shapes, evolution along the jet flow, and jet powers. We also highlight the important role of external photon fields, such as the accretion disk and the BLR.

Speaker: Michael Zacharias (LSW Heidelberg)

Zacharias_ExHaLe_Fermi_2022.pdf

17:15 The blazar hadronic code comparison project

The broad-band multiwavelength spectral energy distribution of blazars consists of two components: the low-energy hump commonly interpreted as synchrotron emission of relativistic electrons accelerated in a parsec-scale magnetized jet and the high-energy component, the nature of which remains debatable, depending on the jet composition. Two main scenarios were developed to shed light on emission of blazars, i.e. leptonic models, in which the radiative emission is dominated by leptons, electrons and positrons, and hadronic models, taking into account both leptons and hadrons. In hadronic models, the gamma-ray emission is associated with synchrotron emission by protons and/or secondary leptons produced in proton-photon interactions, and, together with photons, hadronic emission models predict the emission of neutrinos.
The simulation of proton-photon interactions and all associated radiative processes is a complex numerical task and different approaches to the problem have been adopted in the literature. So far, no systematic comparison between the different codes has been performed, preventing a clear understanding of the underlying uncertainties in the numerical simulations. To fill this gap, we have undertaken the first comprehensive comparison of blazar hadronic codes, and the results from this effort will be presented in this contribution.

Speaker: Natalia Żywucka

Code_comparison_new.pdf

16:00 → 17:30 Parallel 6: Pulsars II

Convener: Dr Andrey Timokhin (University of Zielona Góra)

16:00 Visualizing the pulsar population using graph theory

The $P\dot P$ diagram is a cornerstone of pulsar research. It is used in multiple ways for classifying the population, understanding evolutionary tracks, identifying issues in our theoretical reach, and more. However, we have been looking at the same plot for more than five decades. A fresh appraisal may be healthy. Is the $P\dot P$-diagram the most useful or complete way to visualize the pulsars we know? Here we pose a fresh look at the information we have on the pulsar population. First, we use principal components analysis over magnitudes depending on the intrinsic pulsar's timing properties (proxies to relevant physical pulsar features), to analyze whether the information contained by the pulsar's period and period derivative is enough to describe the variety of the pulsar population. Even when the variables of interest depend on $P$ and $\dot P$, we show that $P\dot P$ are not principal components. Thus, any distance ranking or visualization based only on $P$ and $\dot P$ is potentially misleading. Next, we define and compute a properly normalized distance to measure pulsar nearness, calculate the minimum spanning tree of the population, and discuss possible applications. The pulsar tree hosts information about pulsar similarities that go beyond $P$ and $\dot P$, and are thus naturally difficult to read from the $P\dot P$-diagram. We use this work to introduce the pulsar tree website http://www.pulsartree.ice.csic.es containing visualization tools and data to allow users to gather information in terms of MST and distance ranking. We also discuss applications of these techniques to the Fermi-LAT pulsar catalog.

Speaker: Diego F Torres (ICREA & ICE, CSIC)

Torres_pulsartree.pdf

16:15 Gamma-ray Eclipses and Orbital Modulation Transitions in the Candidate Redback 4FGL J1702.7-5655

Observations with the Fermi Large Area Telescope (LAT) of the gamma-ray source 4FGL J1702.7-5655, previously classified as a candidate millisecond pulsar, show highly-significant modulation at a period of about 6 hours. The folded light curve shows the presence of narrow eclipses and this is thus likely to be orbital modulation in a redback binary system. An examination of the long-term properties of the modulation over 13 years of LAT observations indicates that the orbital modulation of the gamma-rays changed from a simple eclipse before early 2013, to a broader quasi-sinusoidal modulation. In addition, the time of the eclipse shifts to ~0.05 later in phase. This change in the orbital modulation properties is, however, not accompanied by a significant overall change in gamma-ray flux or spectrum. The quasi-sinusoidal component peaks ~0.5 out of phase with the eclipse, which would indicate inferior conjunction of the compact object in the system. Swift X-ray Telescope observations reveal a possible X-ray counterpart within the Fermi error ellipse. However, radio observations obtained with the Australia Telescope Compact Array do not detect a source in the region. 4FGLJ1702.7-5655 appears to have changed its state, perhaps related to changes in the intrabinary shock in the system. We discuss how the properties of 4FGLJ1702.7-5655 compare to other binary millisecond pulsars that have exhibited orbital modulation in gamma rays. Chandra observations have also been approved and will be carried out before the symposium, and we will provide a preliminary report on these.

Speaker: Robin Corbet

1702_10thFermi_Symposium.pptx

16:30 Modelling the high-energy curvature radiation for the Vela pulsar using a general particle dynamics approach.

AR Sco is a binary system that contains both a white and red dwarf. The spin rate of the white dwarf has been observed to slow down with time, analogous to rotation-powered radio pulsars; it has thus been dubbed a "white dwarf pulsar". We have constructed a sophisticated emission model, solving the particle dynamics from first principles, including a generalized radiation reaction force, and implementing similar techniques to what were used in a pulsar emission code developed by A.K. Harding and collaborators to produce emission maps, light curves and spectra. Additionally, our model is able to probe non-relativistic motion and is thus suitable for magnetic mirror scenarios.
We present our calibration results of the two codes by applying them both to the Vela pulsar. Using the same curvature-radiation calculations as Harding et al. our generated emission maps, spectra and light curves are compared to their results to confirm that our photon phase correction calculations and emission mapping techniques are correct. We can also investigate the effect that the approximations of (i) super-relativistic particles with small pitch angles and (ii) time-averaged pitch angles have on the predictions. Once thus calibrated, we can confidently construct emission maps, light curves, and spectra for AR Sco for much lower Lorentz factors and more generic particle motions.

Speaker: Louis du Plessis

L_Du_Plessis_Fermi2022_conference.pdf

16:45 Statistical Goodness and Utility: Lessons learned from multiband pulsar light curve fits

Joint multiband model fits to observed pulsar light curves (LCs) hold the potential to yield tight constraints on a variety of pulsar parameters (e.g., the magnetic inclination $\alpha$; compared to single-band fits) for a variety of pulsars. This potential is arguably yet unrealised in many cases, though, typically due to a substantial imbalance across wavebands in the observed LCs' precision. For example, constraints derived via joint fits to observed radio and $\gamma$-ray LCs are often radio-dominated, and indistinguishable from those derived via radio-only fits. As yet, no definitive solution to this problem has been found.

In this talk we discuss the core lessons we learned while investigating the multiband fitting problem. Most prominent among these is that what lies at the centre of this problem is a general misunderstanding of the role played by the various likelihood-related statistics we use to conduct multiband fits (e.g., Pearson's $\chi^2$ statistic, often used to gauge goodness-of-fit); these statistics are used as proxies for appropriate utility functions/statistics. As we aim to demonstrate in this talk, however, this insight is no condemnation of likelihood-related statistics. We argue that such statistics generally complement other utility statistics, and aim to demonstrate this via a case study of the joint fits to the radio and $\gamma$-ray LCs observed for PSR J2039$-$5617, reported in Corongiu et al. (2020) and conducted using the $\Psi^2_{\Phi,\mathrm{c}}$ statistic to gauge utility.

Speaker: Albertus Seyffert

aseyffert_fermi2022_slides.pdf

17:00 ENHANCEMENTS AND OPERATION OF AN ACCRETING PULSAR PROGRAM Over the last 11 years USING GBM DATA

The Fermi Gamma ray Burst Monitor (GBM) is a unique instrument that offers the largest instantaneous field of view of any hard X-ray instrument currently in operation. This capability along with excellent timing resolution, makes it very successful at detecting rare transient events as well as providing long integration times for pulsed signal extraction. Even though GBM has a relatively modest size, the GBM Accreting Pulsar Program (GAPP) is able to observe a typical accreting pulsar for up to 45,000 seconds each day allowing us to make precise measurements of the source frequency and pulsed flux for sources with a spin frequency between 0.001 and 2 Hz. These frequency measurements along with GBM’s excellent timing capabilities have given us the capability to determine/update orbital ephemerides for many sources as well as monitor rare torque reversals in persistent (semi-persistent) sources such as EXO 2030+375. Continuous Time Tagged Event data, available since November 2012, allows GAPP to track the frequency of even higher frequency sources and we plan to make these histories available this year.

The GAPP consists of two parts: A daily blind search which looks for excess power in the Fourier spectrum from 15 equally spaced directions along the Galactic plane plus the directions to the SMC and LMC and a dedicated monitoring program for 43 sources, in which 39 have been detected including SMC X-3. The results of the dedicated monitoring program are available online (http://gammaray.msfc.nasa.gov/gbm/science/pulsars.html) and updated twice a week.

We will present 11 years of accreting pulsar monitoring with Fermi/GBM and show how GAPP is providing new insight into these sources.

Speaker: Peter Jenke (University of Alabama in Huntsville)

GAPP_10thFSymp.pdf

GAPP_10thFSymp.pptx

17:15 _

Wednesday 12 October

09:00 → 10:30 Plenary 5: Dark Matter, Diffuse, Solar

Convener: Dr Regina Caputo (GSFC/UMCP)

09:00 Fermi/eRosita bubbles as relics of the past activity of Sgr A*

Fermi bubbles and the newly discovered eRosita X-ray bubbles are gigantic bubbles above and below the Galactic center (GC) in the Milky Way Galaxy. Their symmetry suggests that they originate from energetic outbursts from the GC; however, whether it is linked to a nuclear starburst or black hole activity has been intensely debated. Here I present our recent results using 3D hydrodynamic simulations including relevant cosmic-ray physics and show that the multi-wavelength morphology and spectra of the Fermi/eRosita bubbles as well as the microwave haze could be simultaneously explained by past jet activity of the Sgr A* several Myr ago. I will also discuss the constraints derived from our simulations as well as the implications of the results.

Speaker: Hsiang-Yi Karen Yang

09:30 Indirect Dark Matter Searches with Fermi-LAT

With over 14 years of data collection, many dark matter (DM) searches have been performed with Fermi-LAT. Notably, a systematic excess of gamma rays has been detected coming from the Galactic Center (GC) region, and the current leading explanations include mis-modeling of the Galactic diffuse emission along the line of sight, emission from a sub-threshold source population such as millisecond pulsars, and/or WIMP DM annihilation. However, no complementary signal has yet been detected from a combined analysis of the Milky Way dwarf spheroidal satellite galaxies, and numerous studies have placed upper limits on the DM annihilation cross section. These upper limits remain one of the most robust and stringent constraints from indirect DM searches and, specifically, they are crucial for DM interpretations of the GC excess. Other complementary studies have provided competitive and independent upper limits as well, including those obtained from dwarf irregular galaxies, the Large and Small Magellanic Clouds, Galactic DM subhalos, the Milky Way halo, M31, galaxy clusters, the extragalactic gamma-ray background, and DM signals towards the Sun. Limits have also been placed on models of axion-like particles (ALPs), in this case looking for ALP-induced spectral distortions in LAT data. In this talk I will give a broad overview of these past results and also discuss future prospects for indirect DM searches with the LAT.

Speaker: Christopher Michael Karwin

Karwin_Fermi_Symposium_2022.pdf

10:00 Gamm-ray Emission from the Sun

Sustained gamma-ray emission (SGRE) from the Sun represent emission extending up to a day beyond the impulsive phase of solar flares. SGRE was first identified by Forrest et al. (1985) using data from the Solar Maximum Mission’s Gamma-Ray Spectrometer. Only a handful of SGRE events were known over the next thirty years until the advent of the Fermi-Large Area Telescope (LAT). Fermi/LAT has detected more than three-dozen of these events, which help us obtain their statistical properties and their association with solar eruptive events. These events help us understand the origin of >300 MeV protons that interact with the solar chromosphere, produce neutral pions, which decay into the observed gamma-rays. SGRE events are associated with solar flares of X-ray class M and X, large solar energetic particle (SEP) events, interplanetary type II radio bursts, and superfast (>2000 km/s) coronal mass ejections (CMEs). All these eruptive phenomena are related to one another. Energetic CMEs drive shocks that accelerate protons observed as SEPs and electrons resulting in type II bursts. Flares and CMEs are two aspects of energy release in solar magnetic regions. Particles are also accelerated in the flare reconnection region, which is spatially compact. The flare particles are responsible for various impulsive phase emissions including gamma-rays, which have properties different from those of SGREs. Some authors attribute even SGREs to flare-accelerated protons trapped in flare loops, although their close connection to SEPs, type II bursts, and CMEs point to an extended source, viz., the shock driven by CMEs. In this talk, I will review the properties of SGRE events and the associated phenomenon and the current understanding of the emission mechanism.

Speaker: Dr Nat Gopalswamy (NASA Goddard Space Flight Center)

10:30 → 11:00 Coffee Break

Posters

11:00 → 13:00 Plenary 6: GRB & GW

Convener: Makoto Arimoto

11:00 Electromagnetic radiation from binary neutron star mergers

Joint detection of GW and EM from binary neutron star merger provides enormously more information than detection of the GWs or the EM alone. This was beautifully demonstrated by the recent LVC runs and the comparison of GW 170817 with its EM counterparts and GW 190425 for which those weren't discovered. The EM radiation from binary neutron star mergers includes several distinct sources: The prompt gamma-ray burst, the cocoon breakout, the afterglow and the kilonova. Combining information from GRB 170817A, GW 190425 and from the population of short GRBs I compare the detectability of the different components of the emission and estimate the chances and rates of joint detection of GWs and EM from future mergers.

Speaker: Tsvi Piran (The Hebrew University)

PIRAN_FERMI22.pptx

11:30 Very-high-energy gamma rays from gamma-ray bursts

The study of gamma-ray bursts (GRBs) is often advanced by detections of individual spectacular events. In the last few years, very-high-energy (VHE, >100 GeV) emission from GRBs has been detected for the first time, allowing us to build a multiwavelength picture of GRBs that extends all the way up to TeV energies. In this talk, I will give an overview of the current state of VHE GRB detections, and the potential implications for the 'standard' model of GRB emission.

Speaker: Sylvia Jiechen Zhu

sjzhu_VHEGRBs_betterRes.pdf

sjzhu_VHEGRBs.pdf

12:00 Fermi GBM - 14 years in operation

I will report on the current instrument status, ongoing and planned projects, and recent results.

Speaker: Andreas von Kienlin (MPE)

10thFermiSymp_FermiGBM_vKienlin.pdf

12:15 Searching for GRB Counterparts to Gravitational-wave Events from the Third Gravitational Wave Observing Run with Fermi-GBM and Swift-BAT

We present Fermi Gamma-ray Burst Monitor (Fermi-GBM) and Swift Burst Alert Telescope (Swift-BAT) observations of gravitational-wave (GW) events detected during the third LIGO/Virgo/KAGRA Collaboration observing run (O3). Using Fermi-GBM on-board triggers as well as sub-threshold searches in both Fermi-GBM and Swift-BAT ground data, we search for coincident gamma-ray transients associated with the GW events. No new joint events beyond GRB 170817A and GW170817 were found. We therefore calculate flux upper limits for the associated gamma-ray luminosity of each GW event. Using the lack of electromagnetic (EM) emission from binary black hole (BBH) mergers, we begin to constrain theoretical models of any such emission.

Speaker: Joshua Wood (NASA/MSFC)

Wood Fermi Symposium Slides.pdf

12:30 Onset of particle acceleration during the prompt phase in GRBs

The physical processes of the gamma-ray emission and particle acceleration during the prompt phase in GRBs are still unsettled. In order to perform an unambiguous physical modelling of GRB observations, a clear identification of the emission mechanism is essential. The very strong flare in GRB160821A, that occurs during the prompt phase at 135s, has for instance been clearly identified as synchrotron emission. By using Fermi observations, we show that the distribution of the radiating electrons is initially very narrow, but later develops a power-law tail of accelerated electrons. We thus identify for the first time the onset of particle acceleration in a GRB jet. The flare is consistent with a late energy release from the central engine causing an external-shock as it encounters a preexisting ring nebula of a progenitor Wolf-Rayet star. Relativistic forward and reverese shocks develop, leading to two distinct emission zones with similar properties. The particle acceleration only occurs in the forward shock, moving into the dense nebula matter. Here the magnetisation decreases below the critical value which allows for Fermi acceleration to operate. The observation of the onset thus gives new and independent constraints on the properties of the flow as well as on theories of particle acceleration in collisionless astrophysical shocks. For the prompt flare in GRB160821A we find a bulk Lorentz factor of Gamma \sim 640 and an emission radius of R \sim 10^{18} cm, consistent with a Wolf-Rayet ring nebula with a hot, tenuous phase of its interior.

Speaker: Felix Ryde

FelixRydeTalk_Fermi2022.pdf

12:45 Probing into emission mechanisms of GRBs using time-resolved spectra and polarization studies

The emission processes responsible for the prompt emission of gamma-ray bursts (GRBs) are still an open question. Besides temporal and spectral properties, hard X-ray/ gamma-ray polarization measurement is thought to be a powerful tool for probing the radiation mechanisms of GRBs since the emission mechanisms invoked to explain prompt emission are associated with unique polarization signatures. Therefore, a detailed time-resolved spectro-polarimetric investigation of the prompt emission could provide insights into this long debatable problem. This work presents the timing, spectral, and polarimetric analysis of the prompt emission of bright bursts (specifically GRB 190530A) observed using the Cadmium Zinc Telluride Imager (CZTI) onboard AstroSat and Fermi gamma-ray space telescope to provide insight into the prompt emission radiation mechanisms. By performing a detailed time-resolved spectro-polarimetric study of these GRBs, we could pin down their elusive prompt emission mechanisms.

In the case of multi-pulsed GRB 190530A, the time-integrated spectrum shows conclusive proof of two breaks due to peak energy and a second lower energy break. Time-integrated (55.43 +/- 21.30 %) as well as time-resolved polarization measurements made by the CZT-Imager onboard AstroSat, show a hint of a high degree of polarization. The presence of a hint of the high degree of polarization and the values of low energy spectral index (ɑ) do not run over the synchrotron limit for the first two pulses, supporting the synchrotron origin in an ordered magnetic field. However, during the third pulse, ɑ exceeds the synchrotron line of death in a few bins, and a thermal signature along with the synchrotron component in the time-resolved spectra is observed. Furthermore, we also report the earliest optical observations constraining afterglow polarization using the MASTER (P < 1.3 %) and the redshift measurement (z= 0.9386) obtained with the 10.4m GTC telescopes.

Speaker: Rahul Gupta (Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital-263002, India)

Rahul_10thFSymp.pdf

13:00 → 14:00 Lunch

14:00 → 14:15 Poster session

AGN - GRBs - SNR/PWNe - Future Missions/Instruments - Analysis Techniques - Pulsars - Binaries - Neutrinos - Diversity and Equity - Dark Matter - Solar System Gravitational Waves

14:15 → 15:30 Parallel 7: Dark Matter

Convener: Christopher Michael Karwin

14:15 Detection forecasts for annihilating DM in M31 and M33 galaxies with the Cherenkov Telescope Array

M31 and M33 are the closest spiral galaxies and the largest members (together with the Milky Way) of the Local group, which makes them interesting targets for indirect dark matter searches. In this paper we present studies of the expected sensitivity of the Cherenkov Telescope Array (CTA) to an annihilation signal from weakly interacting massive particles from M31 and M33. We show that a 100 h long observation campaign will allow CTA to probe annihilation cross-sections up to $\langle\sigma\upsilon\rangle\approx5\cdot10^{-25}~\mathrm{cm^{3}s^{-1}}$ for the $\tau^{+}\tau^{-}$ annihilation channel (for M31, at a DM mass of 0.3 TeV), improving the current limits derived by HAWC by up to an order of magnitude.
We present a robust estimate of the expected CTA sensitivity, by also taking into account the contributions of the astrophysical background and other possible sources of systematic uncertainty.
We show that CTA might be able to detect the extended emission from the bulge of M31, detected at lower energies by the Fermi/LAT.

Speaker: Miltiadis Michailidis

14:30 Connecting astrophysics and the LHC with anomalies

Anomalies in multi-lepton data from the Large Hadron Collider (LHC) have been used to motivate for an extension to the Standard Model in the form of a second Higgs doublet and a singlet scalar (2HDM+$S$). Here we explore a dark matter candidate drawn from this model: a scalar particle that couples to the Standard Model through the 2HDM+$S$ degrees of freedom. Using the best-fit 2HDM+$S$ model from LHC data, and consequent dark matter annihilation/decay yields, we will study the general constraining power of Fermi-LAT data on this model. In particular, we will see if Fermi-LAT data impacts the parameter space used to explain various astrophysical excesses in previous work. This study is part of a project exploring potential connections between collider and astrophysical excesses, thus seeking to illustrate new synergies between large and small-scale probes beyond the Standard Model as well as those between the MeerKAT/SKA and high-energy astrophysics experiments.

Speaker: Geoff Beck

slides_gbeck_10thFSymp.pptx

14:45 The GeV Galactic Center Excess in 2022

The Galactic center excess (GCE) remains one of the most intriguing discoveries from the Fermi Large Area Telescope (LAT) observations. I will revisit characteristics of the GCE tested under an updated set of high-resolution galactic diffuse gamma-ray emission templates. This diffuse emission, which accounts for the bulk of the observed gamma rays, is ultimately due to cosmic-ray interactions with the interstellar medium. Using recent high-precision cosmic-ray observations, in addition to the continuing Fermi-LAT observations and observations from lower energy photons, we constrain the properties of the galactic diffuse emission. A large set of diffuse gamma-ray emission templates has been used which account for a very wide range of initial assumptions on the physical conditions in the inner galaxy. In addition, I will present how wavelet-based techniques allow us to probe and remove the emission form sub-threshold point sources at low latitudes. I will give an update on the spectral and morphological properties of the GCE and their physical implications. In particular, a high-energy tail is found at a higher significance than previously reported. This tail is very prominent in the northern hemisphere, and less so in the southern hemisphere. This strongly affects one prominent interpretation of the excess: known millisecond pulsars are incapable of producing this high-energy emission, even in the relatively softer southern hemisphere, and are therefore disfavored as the sole explanation of the GCE. The annihilation of dark matter particles of mass $40^{+10}_{-7}$ GeV (95$\%$ CL) to $b$ quarks with a cross-section of $\sigma v = 1.4^{+0.6}_{-0.3} \times 10^{-26}$ cm$^{3}$ s$^{-1}$ provides a good fit to the excess especially in the relatively cleaner southern sky. Dark matter of the same mass range annihilating to $b$ quarks or heavier dark matter particles annihilating to heavier Standard Model bosons can combine with millisecond pulsars to provide a good fit to the southern hemisphere emission as well, as can a broken power-law spectrum which would be related to recent cosmic-ray burst activity.

Speaker: Dr Ilias Cholis (Oakland University)

Fermi_2022_Cholis.pdf

15:00 Constraining the Dark Matter annihilation cross section with a combined analysis of dwarf spheroidal galaxy observations from Fermi-LAT, HAWC, H.E.S.S., MAGIC, and VERITAS

The nature of Dark Matter (DM) is still an open question. This elusive kind of matter cannot be made of any of the known particles of the Standard Model (SM) of particle physics. Among the candidates proposed to explain the nature of DM, weakly interacting massive particles (WIMPs) are one of the preferred ones. They could be detected indirectly by observing the products of its annihilation into SM particles and gamma rays. This has led to extensive observing campaigns with ground-based and space-based gamma-ray telescopes. Limits on the DM self-annihilation cross section have been obtained independently by the Fermi-LAT, HAWC, H.E.S.S., MAGIC, and VERITAS collaborations from various DM targets. To maximize the sensitivity of DM searches, we have performed a joint likelihood analysis combining observations of dwarf spheroidal galaxies (dSphs) taken with these telescopes. We will present here the limits obtained to the DM self-annihilation cross section as a function of the DM particle mass, ranging from 5 GeV to 100 TeV.

Speaker: Tjark Miener (IPARCOS, UCM)

GloryDuck_10thFermiSymposium_TjarkMiener_v3.pdf

15:15 Solar dark matter scattering constraints with the Fermi Large Area Telescope

Dark matter (DM) particles from the Galactic halo can be gravitationally trapped by the Sun, where they might annihilate into long-lived mediators, which are able to escape from the Sun and decay into different channels, with the production of gamma rays in the final states. All these processes are expected to yield an excess in the gamma-ray energy spectrum towards the Sun. We have implemented a dedicated analysis using a 13.5-years sample of gamma-ray events from the Sun collected by the Fermi Large Area Telescope, searching for possible signatures of these processes. Since no statistically significant excess is found, we have set upper limits on the signal intensity, which have been converted into constraints on the DM-nucleon scattering cross section for DM masses between a few GeV/$c^2$ up to 1TeV/$c^2$. The limits are in the range $10^{-45}$ to $10^{-39}~cm^2$ for the spin-dependent scattering and in the range $10^{-47}$ up to $10^{-42}~cm^2$ for the spin-independent case. The range of variation depends on the mediator decay channel considered and on its decay length.

Speaker: Davide Serini (Universita e INFN, Bari (IT))

FermiSymposium_DSerini.pdf

14:15 → 15:30 Parallel 8: Solar

Convener: Nicola Omodei (Stanford University)

14:15 Fermi LAT observation of the Moon

We have reconstructed the gamma-ray flux from the Moon in the energy range from 30 MeV up to a few GeV using a 14-years dataset collected by the Fermi Large Area Telescope since its launch in 2008. Gamma rays from the Moon are originated in the interactions of cosmic-ray nuclei with the regolith of the lunar surface and their flux is sensitive to solar activity, which modulates the charged cosmic-ray fluxes in the solar system. We have studied the time evolution of the lunar gamma-ray emission over a period exceeding a solar cycle, and we have found a strong correlation with the solar activity. We have also developed a model, based on the FLUKA simulation code, to evaluate the yields of lunar gamma rays produced by cosmic-ray protons and helium nuclei. We have then folded the yields obtained from the model with the primary proton and helium spectra measured by the AMS-02 and PAMELA experiments in different epochs and we have found that the simulation correctly reproduces the time evolution of the lunar gamma-ray flux.

Speaker: Francesco Loparco (Universita e INFN, Bari (IT))

Symposium_Loparco_v1.pdf

Symposium_Loparco_v1.pptx

14:30 Study of gamma rays from the Small Solar System Bodies with the Fermi-LAT data

All known small Solar System bodies have a diameter between 1 m and a few thousands of km. Based on the collisional evolution of Solar System bodies, a model predicting the existence of a larger number of asteroids with diameters down to 10 m has been suggested. In this work, we propose an extension of this model to diameters of a few cm. Like all Solar System bodies, asteroids can be passive sources of high-energy gamma rays, which are produced when energetic charged cosmic rays impinge on their surfaces. Since the majority of known asteroids lie in an orbit between Mars and Jupiter (known as the Main Belt), we expect them to produce a diffuse emission close to the ecliptic plane. In this work, we have studied the gamma-ray emission from the ecliptic by using the data collected by the Large Area Telescope (LAT) onboard the Fermi satellite. We have fitted the LAT data with a template model for the diffuse emission of small Solar System bodies obtained with a dedicated simulation based on the FLUKA Monte Carlo toolkit. The fit results provide an upper limit on the total flux, which yields a constraint on the asteroid population model.

Speaker: Mr Salvatore De Gaetano (INFN sezione di Bari, Università degli Studi di Bari "Aldo Moro")

Tenth_Fermi_Symposium_De_Gaetano.pptx

14:45 _

15:00 Investigation of Coronal Mass Ejection Driven Shock in Relation to the Fermi-LAT Long-Duration Solar Flares using Data-driven Global MHD Simulations

The increasing number of long-duration gamma-ray solar flares >100 MeV observed by Fermi/LAT poses a puzzle on the particle acceleration and transport mechanisms. Since most of the long-duration events are associated with fast coronal mass ejections (CMEs), it is therefore intriguing to understand the role of CMEs and CME-driven shocks in these events. In this study, we perform data-driven, global MHD simulations of the CMEs associated with 8 Fermi-LAT long-duration solar flares. We derive and track the time-varying shock parameters over the area that is magnetically connected to the gamma-ray emission region. The CME-driven shock properties are then compared with the observational quantities of the Fermi-LAT delayed phase emission including peak flux and decay timescale. Our result shows that the simulated shock parameters are well correlated with the characteristics of the delayed phase emission, which suggests the CME-driven shock and shock accelerated particles play an important role in these delayed emission of gamma-ray solar flares.

Speaker: Meng Jin

15:15 Cosmic Ray Electron Transport and Radiation in the Inner Heliosphere and X-ray and Gamma-ray Observations of the Quiet Sun

Fermi routinely observes gamma-rays from the quiet Sun (QS), i.e. when there is no flaring activity, and there are upper limits in X-ray regime from RHESSI. The gamma-rays are produced by Cosmic Ray (CR) protons (via pion production) and electrons via inverse Compton (IC) scattering of solar optical photons. This problem has received considerable attention. A possible source of the X-rays could be synchrotron emission by Cosmic Ray Electrons (CRes) which has not received much attention. Fluxes and spectra of CRs are observed at 1 AU, but calculation of QS radiation requires flux-spectrum of CRs from the Earth to the Sun. The common practice to this end is to use some phenomenological modulation procedure. This procedure may be useful for evaluation of the CRs variation in the outer (>1 AU) heliosphere, but the transport from one AU to the Sun requires a kinetic approach, because particle paths are determined by the large scale magnetic field. We address this transport using a Fokker-Planck equation including the effects of field convergence, scattering by turbulence and more important for CRes, the energy loss rate due to synchrotron and IC processes.

Several near Earth instruments have observed CRe spectra at 1 AU during quiet and active phase of the Sun. There are also many observations and subsequent models for the structure of the magnetic field in the inner heliosphere, which allow us to address the first and third processes fairly accurately. However, the second requires a knowledge of the energy density and spectrum of turbulence from 1 AU to the Sun. Up to recently these characteristics of the turbulence were measured around 1 AU, but Parker Solar Probe (PSP) has extended this knowledge to 0.17 AU, which can be extrapolated to the Sun using several reasonable models. In this talk we will present result on transport of CRes using a novel and simple version of Fokker Planck equation, and will present the spectral evolution of the CRes from 1 AU to the photosphere, for three models of the turbulence. The spectra at the photosphere can then be used to calculate, for the first time, the synchrotron spectrum and a more accurate IC spectrum, which when used in conjunction with gamma-ray and X-ray observations can constrain the transport processes and their parameters.

Speaker: Vahe' Petrosian (Stanford University)

15:30 → 16:00 Coffee Break

Posters

16:00 → 17:45 Parallel 10: GRBs and Fast Transients- I

Convener: Dr Andreas von Kienlin (MPE)

16:00 GeV emission from a compact binary merger

The origin of gamma-ray bursts (GRBs) is still mysterious. We believe that binary neutron star (BNS) mergers produce short GRBs, while long GRBs are associated to the collapse of massive stars.

This GRB dichotomy, based on the duration of the prompt pulse, was recently challenged by the detection of the bright and relatively close (z=0.076) GRB 211211A. Despite its long duration (~30 s), the discovery of an optical-infrared kilonova (KN) points to a compact object binary merger origin.

We have analysed the radio-to-GeV afterglow emission of this source. In particular, the analysis of the high energy (HE, 0.1-10 GeV) data, provided by Fermi/LAT, revealed a significant emission (> 5sigma) detected in two epochs at late times (~10^3 and ~10^4 s after the burst) with approximately constant flux (~5e10 erg/cm^2/s).

The multi-wavelength afterglow emission is well modelled by synchrotron emission from electrons accelerated in the forward shock (FS). The model includes also the optical/NIR KN emission, which accounts for the excess in the r-band, and synchrotron-self-Compton, which is not dominant at these energies (< 10 GeV).
Nonetheless, the LAT emission in the second epoch (~10^4 s) is in substantial excess with respect to the FS+KN best-fit model.

This intrinsically faint excess (Liso~10^46 erg/s) was never observed before in neither short nor long GRB populations.

We interpret this new spectral component as external Inverse Compton (EIC) emission from KN optical photons and electrons accelerated in the low-power jet.

The discovery of the late-time HE excess in GRB 211211A strongly challenges our current understanding
of emission processes occurring in gamma-ray burst, especially at high energies, and opens a new observational window for kilonovae, which can possibly be observed also in the ~GeV spectrum.

Speaker: Alessio Mei (Gran Sasso Science Institute)

mei_fermi_symposium.pdf

16:15 The Gravitational Wave-Gamma Ray Burst Working Group and InterPlanetary Network in O4

LIGO, Virgo, and KAGRA will begin the fourth gravitational wave observing run in March 2023. Gamma-ray burst identification and localization are key to multimessenger studies with neutron star mergers, with scientific results spanning from fundamental physics to ultrarelativistic particle acceleration. We will detail the partnership and plans of the gravitational wave collaborations with Fermi and Swift, as well as steps to modernizing the InterPlanetary Network of GRB-observing satellites with a focus on the O4 observing run.

Speaker: Eric Burns

GW_GRB_and_IPN_v3.pdf

GW_GRB_and_IPN_v3.pptx

16:30 Discovery of high-energy gamma-ray emission from a reverse shock of GRB 180720B

Gamma-ray bursts (GRBs) emit cosmic high-energy gamma rays over a short period of time and the origin of gamma rays is still under debate. Recent gamma-ray observations in the GeV and TeV bands by Fermi and MAGIC revealed that some of the high-energy gamma rays are thought to originate from the forward shock of GRB jets. However, early-stage bright gamma-ray emissions are still poorly understood and cannot be explained by only the forward shock of relativistic ejecta. One of the possible origins is a reverse-shock emission, but there has been no distinct evidence so far. Here, we present the discovery of gamma-ray emission originating from the reverse shock coincident with the optical emission from GRB 180720B. The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope detected bright gamma-rays lasting for >100 s in the GeV band while the Kanata telescope simultaneously detected bright optical emission. The observed temporal and spectral behaviors in the optical and GeV bands at the early phase can be interpreted as a reverse-shock component: relativistic electrons scatter optical synchrotron photons serving as seed photons and inverse-Compton GeV emission is created in the reverse shock. This result suggests that not only the forward shock but also the reverse shock is crucial for explaining the origin of the high-energy gamma-ray emission.

Speaker: Makoto Arimoto

FermiSymposium_Tenth_GRB180720B_arimoto_v1.pdf

16:45 Intergalactic magnetic field studies by means of the gamma-ray emission from GRB 190114C

The origin of the large-scale magnetic fields in the Universe is one of the long-standing problems in cosmology. To discriminate among the different explanations it is crucial to measure the intergalactic magnetic field (IGMF) in the voids among the galaxies. Gamma-rays coming from extragalactic sources can be used to constrain the IGMF due to their interaction with the intergalactic medium. Particularly, strong transients allow to constrain very weak IGMFs. We use CRPropa3 to propagate the measured very-high energy (E > 100 GeV) spectrum from GRB 190114C in the intergalactic medium. We then compute the expected cascade emission in the GeV domain for different IGMF settings and compare it with the Fermi/LAT limits for different exposure times.

Speaker: Francesco Longo

IGMF_GRB_10thFSymp_Longo.pdf

17:00 A wind environment and Lorentz factors of tens explain gamma-ray bursts X-ray plateau

Gamma-ray bursts (GRBs) are known to have the most relativistic jets, with initial expansion Lorentz factors of 100< Gamma_i <1000. Many of these objects have a plateau in their early X-ray light curves (up to thousands of seconds). In this phase, the X-ray flux decreases much slower than theoretically expected which has puzzled the community for many years. Here, we show that the observed signal during this phase in both the X-ray and the optical bands is naturally obtained within the classical GRB “fireball” model, provided that (i) the initial Lorentz factor of the relativistically expanding jet is of the order of a few tens, rather than a few hundreds, and (ii) the expansion occurs into a medium-low density “wind” with density typically up to two orders of magnitude below the expectation from a Wolf-Rayet star. Within this framework, the end of the “plateau” phase marks the transition from the coasting phase to the self-similar expansion phase. We also show that difference in the Lorentz factor not only manifest itself in the afterglow phase, but also manifest in the prompt emission. Here, we discuss the implication of the results on the properties of GRB progenitors and the resulting jets, and show how they provide a novel tool to infer the physical properties inside the jet.

Speaker: Dr Hüsne Dereli Bégué (Bar-Ilan University)

10thFSymp_Husne_Dereli-Begue.pdf

17:15 The Search for Extra-Galactic Magnetar Giant Flares in Fermi GBM Data

Magnetars are a type of neutron star characterized by strong (10^14 − 10^15 G), short-lived (∼ 10^4 yr) magnetic fields. They display a range of high energy electromagnetic activity. The brightest and most energetic of these events, with Eiso ≈ 10^44 − 10^46 erg, is the magnetar giant flare (MGF). To date only 7 such events have been discovered, 3 of which occurred in our galactic neighborhood. The detections for the 3 local events suffered from instrument saturation. This means the best chance for studying MGFs resides in building a population of extra-galactic events. Given inferred volumetric event rates for galaxies with star formation rates similar to the Milky Way, it stands to reason that there may be more such events recorded in archival data. Therefore, a search of Fermi GBM data was conducted. We will detail the status of our search of these data for more MGFs.

Speaker: Aaron Trigg

A_Trigg_10thFSymp.pptx

17:30 Hunting the gamma-ray emission from Fast Radio Bursts with Fermi-LAT

Fast radio bursts (FRBs) are one of the most exciting new mysteries of astrophysics. Their origin is still unknown, but recent observations seem to link them to soft gamma repeaters and, in particular, to magnetar giant flares (MGFs). The recent detection of a MGF at GeV energies by the Fermi Large Area Telescope (LAT) motivated the search for GeV counterparts to the >1000 currently known FRBs. To date, none of these has a known gamma-ray counterpart.

Taking advantage of more than 12 years of Fermi-LAT data, we perform a search for gamma-ray emission from almost all the reported repeating and non-repeating FRBs. We analyze on different time scales the Fermi-LAT data for each individual source separately and perform a cumulative analysis on the repeating ones. In addition, we perform the first stacking analysis at GeV energies of this class of sources in order to constrain the gamma-ray properties of the FRBs. The stacking analysis is a powerful method that allows for a possible detection from below-threshold FRBs providing important information on these objects. In this talk we present the results of our study and we discuss their implications for the predictions of gamma-ray emission from this class of sources.

Speaker: Francesco Longo (University and INFN Trieste)

FRB_search_with_Fermi_LAT.pdf

16:00 → 17:45 Parallel 9: AGN-III

Convener: Andrew Chen

16:00 Redshift Determination of the Hard spectrum Fermi-LAT Gamma-Ray Blazars detectable with CTA

Fermi-LAT has detected more than 3700 gamma-ray blazars, confirming that they are the
largest group of high-energy gamma-ray emitters. In gamma-ray astronomy it is therefore crucial to understand their emission mechanisms and their population properties. In the same way they are also fundamental for indirect studies on topics such as the extragalactic background light and searches for the axion-like particles among others. Despite strong efforts by the astronomical community, unfortunately only about 50 % of BL Lacs, the most numerous class of gamma-ray blazars, have a measured spectroscopic redshift. Due to their nearly featureless optical spectra it is in fact challenging to measure solid redshifts for these objects.

This is particularly problematic for the next generation ground-based VHE gamma-ray observatory CTA which will detect and study a large amount of distant blazars. In preparation for the CTA observations, we devised an observing program aiming to measure the redshifts of bright, hard spectrum gamma-ray blazars that are likely to be detected with CTA. The sample was selected using the Monte Carlo simulations employing spectral parameters from the 3FHL Fermi catalog and public CTA response matrices. We
have been performing spectroscopic and imaging observations in order to constrain the redshifts in the best way possible. The results are published incrementally as a contribution to the gamma-ray community. I will describe the scope of our project, its status and its future developments.

Speaker: Paolo GOLDONI (APC/IRFU)

Redshift Determination of Hard Spectrum Fermi-LAT Blazars for CTA.pptx

16:15 Investigating the temporal behaviour of simulated multi-wavelength blazar variability for coloured noise variations.

It is characteristic of multi-wavelength blazar variability to exhibit temporal signatures of coloured noise. We therefore simulate multi- wavelength blazar variability by means of time-dependent blazar modeling and introduce different generated sets of coloured noise variations. The different sets of variations specifically cover a spectrum of pure power law indices in temporal frequency representative of coloured noise. A correlation in pure power law index between variations and multi-wavelength variability is found. Additionally cases of broken power laws were identified in some wavelengths.

Speaker: Hannes Thiersen

HThiersen-Fermi_Symp_presentation.pdf

16:30 Significant detection of Quasi-periodic Oscillation in gamma-ray blazar

The broadband emission in the blazar is highly anisotropic and non-thermal boosted along the jet axis and dominated by red noise. Any kind of periodic signature in their light curve is buried in the red noise and therefore a sophisticated method is required to detect them if they are present. Recently, the presence of a QPO signal is proposed or detected in the gamma-ray light curve of many blazars, and in some cases detected with above 3$\sigma$ significance with 3-4 cycles. Many models have been proposed to explain the QPO of different time scales.
I will be talking about a blazar where we have detected the QPO signal of range of time scale from a few tens of days to years and more importantly above 4$\sigma$ and above 4 cycles. Our detection of the QPO signal strongly backs the idea of a curved-jet model in a blazar.

Speaker: Raj Prince

Fermi2022_Raj.pdf

16:45 Search for periodicities in irregularly-sampled AGNs with a time-domain approach

This project investigates a new methodology to search for periods in light-curves of high-energy gamma-ray sources such as Active Galactic Nuclei (AGNs). High-energy light curves have significant stochastic components, making period detection somewhat challenging.
In our first model, periodic terms , drifts of the light-curves and random walk with correlation between flux points due to colored noise are taken into account independently. The parameters of the model are obtained directly from a Markov Chain Monte-Carlo minimization. Also, this model allows to study the variability in time of period and amplitude of oscillating terms. This has been already applied to a sub-sample of 27 Fermi-LAT sources and has been published in ApJ.
Now, the algorithm has been developed further to be able to analyze light curves with irregular data or with important gaps between points. This opens the posibility to study all the thousands of AGNs available from Fermi-LAT and not only the small sub-sample with continuos data. Here, we aim to present the methods developed and the results on continuos data, as well as the preliminary results on irregular data.

Speaker: Héctor Rueda (IRFU - CEA Paris-Saclay)

Rueda_FermiSymposium2022.pdf

Rueda_FermiSymposium2022.pdf

Rueda_FermiSymposium2022.pptx

17:00 High energy emission component and population of gamma-ray emitting radio galaxies

In this study, we systematically studied the X-ray to GeV gamma-ray spectra of 61 {\it Fermi} Large Area Telescope (LAT) detected radio galaxies. We found an anticorrelation between peak frequency and peak luminosity in the high-energy spectral component of radio galaxies, similar to blazars. With this sample, we also constructed a gamma-ray luminosity function (GLF) of gamma-ray-loud radio galaxies. We found that blazar-like GLF shapes can reproduce their redshift and luminosity distribution, but the log$N$-log$S$ relation prefers models with more low-$z$ radio galaxies. This indicates many low-$z$ gamma-ray-loud radio galaxies. By utilizing our latest GLF, the contribution of radio galaxies to the extragalactic gamma-ray background is found to be 1--10\%. We further investigated the nature of gamma-ray-loud radio galaxies. Compared to radio or X-ray flux-limited radio galaxy samples, the gamma-ray selected sample tends to lack high radio power galaxies like FR-II radio galaxies. We also found that only $\sim$10\% of radio galaxies are GeV gamma-ray loud. Radio galaxies may contribute to the cosmic MeV gamma-ray background comparable to blazars by considering this fraction and their high-energy spectral shape.

Speaker: Yasushi Fukazawa

221012radiogal.pdf

17:15 A search for Centaurus A-like features in the spectra of Fermi-LAT-detected radio galaxies

Motivated by the detection of a hardening in the γ-ray spectrum from the core of the radio galaxy Centaurus A, this work focuses on the findings of Fermi-LAT observations of radio galaxies to search for similar spectral features. This includes discussion of a number of radio galaxy γ-ray spectral energy distributions to uncover any common characteristics amongst the Fermi-LAT-detected radio galaxies and results from flux variability studies of the Fermi-LAT detected radio galaxies. Finally, ongoing studies and how the Fermi-LAT results provide a glimpse of what radio galaxies we might expect to see with future ground-based IACTs will also be presented.

Speaker: CAMERON,BOYD RULTEN (Durham University)

RULTEN-Fermi-LAT-radio-galaxies-2022-Uploaded.pptx

17:30 A study of the lobes of the radio galaxy Hydra A using MeerKAT observations

The Hydra A radio galaxy is the result of one of the most powerful AGN outbursts known to date. It hosts a pair of 300- kiloparsec diameter radio lobes that have been inflated over multiple generations of activity. Radio observations provide us with a unique perspective for investigating and studying the high-energy particles that reside in the radio lobes. The MeerKAT radio telescope carried out observations of Hydra A, from which we obtained radio maps at several frequencies between 900 MHz and 1500 MHz. The spatial analysis we performed revealed two bright inner lobes, a pair of diffuse outer lobes, and a tail-like region extending outwards from the southern outer lobe. We conducted a spectral analysis by combining the radiative flux densities that we computed using the MeerKAT observations with flux densities we calculated from previous VLA low-frequency observations at 74 MHz and 330 MHz. The spectral analysis showed that the spectrum in the MeerKAT frequency range is well described by a power law and that the tail-like region exhibits a steeper spectral index than the spectral index of the outer lobes. We set constraints on the magnetic field strength and the age of the outer radio lobes through electron spectrum modelling which includes electron ageing.

Speaker: Mika Naidoo

MikaNaidoo_FermisymposiumUPDATED.pdf

Thursday 13 October

09:00 → 17:30 Excursions

Excursions to the Sterkfontein Caves and to the Rhino and Lion Park

17:30 → 18:30 Free Time

18:30 → 21:00 Banquet at the Carnivore

Friday 14 October

09:00 → 10:30 Parallel 11: Diffuse

Convener: Stefan Wagner

09:00 eROSITA on SRG

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the primary instrument on the Spectrum-Roentgen-Gamma (SRG) mission, which was successfully launched on July 13, 2019, from the Baikonour cosmodrome. After the commissioning of the instrument and a subsequent calibration and performance verification phase, eROSITA started a survey of the entire sky on December 13, 2019. I will present an overview of the instrument capabilities, the current status of the mission, and a few selected early science results and the expectations for the survey program, which has completed last December the fourth of its eight planned charts of the whole sky.

Speaker: Andreas von Kienlin (MPE)

10thFermiSymp_eROSITA_AvKienlin.pdf

10thFermiSymp_eROSITA_AvKienlin.pptx

09:15 The Galactic diffuse gamma-ray emission meets the PeV frontier

The Tibet ASγ and LHAASO collaborations recently provided the first evidence of a diffuse γ-ray emission in the Galaxy up to the PeV from the Galactic plane. Due to the challenges this imposes to current theoretical models it is crucial to carefully study different scenarios of diffuse γ-ray production, specially towards the centre of the Galaxy. In particular, the current models of diffuse emissions struggle to reproduce ASγ and LHAASO data.
In this contribution, we show that these measurements seem to favour an inhomogeneous transport of cosmic rays throughout the Galaxy, specially motivated by the measurements of the Fermi-LAT detector. Moreover, we discuss the relevance of non-uniform cosmic-ray transport scenarios and the implications of these results for cosmic-ray physics and show that the energy spectra measured by Tibet ASγ, LHAASO, ARGO-YBJ and Fermi-LAT in several regions of the sky can be consistently described in terms of the emission arising by the Galactic cosmic-ray ``sea''. We also comment on the impact of other possible contributions, as the γ-ray emission from TeV halos or unresolved sources.

Speaker: Pedro De la Torre Luque

PedroDeLaTorre_10thFSymp.pdf

PedroDeLaTorre_10thFSymp.pptx

09:30 Implications from 3-dimensional modeling of gamma-ray signatures in the Galactic Center

The Galactic Center (GC) region has been intensively studied in gamma-rays in the past decades. Fermi LAT has discovered a GeV excess which is not fully understood, and the first detection of a PeVatron by H.E.S.S. indicates the existence of cosmic ray sources providing energies up to a PeV or higher. The emission of TeV gamma rays in the GC is affected by the source position and the distribution of the gas, photons and magnetic field within this region.
For the first time we model the TeV emission in a realistic three-dimensional distribution of gas as well as photon fields and use a complex magnetic field comprising the large-scale field structure and small-scale imprints of molecular clouds as well as non-thermal filaments. Additionally, we test different anisotropies of the diffusion tensor defined by the ratio of the diffusion coefficients perpendicular and parallel to the local magnetic field direction. For comparison we compute a two-dimensional gamma-ray distribution and compare it with H.E.S.S. measurements.

Speaker: Julien Dörner (Ruhr University Bochum)

Doerner_GalacticCenter.pdf

Doerner_GalacticCenter.pptx

09:45 Investigating the nature of the 4FGL soft Galactic unassociated sources

The bulk of the |b|<10° 4FGL unassociated sources exhibit very soft spectra (power-law index distribution peaking around 2.6), have a Galactic-latitude distribution extending out to 10 degrees, and present notable clustering. These peculiar features, unseen in any classes of associated sources, raise the question of their possible spurious character and of their nature if real. We will outline the properties of these soft sources (referred to as SGUs) and present preliminary results of simulations exploring the possibility that SGUs arise from mismodelled diffuse emission. Inspecting the broad-band environment of the brightest SGUs is a complementary approach to shedding light on their nature.

Speaker: benoit Lott (LPI2B)

SGUs_Symposium_2022_v1.pdf

SGUs_Symposium_2022_v1.pptx

10:00 Gas and Cosmic-Ray Properties in the MBM 53-55 Molecular Clouds and the Pegasus Loop as Revealed by HI Line Profiles, Dust, and Fermi-LAT Gamma-Ray Data

Although diffuse gamma-ray emission is a powerful probe to study the interstellar medium (ISM) and Galactic cosmic rays (CRs), the uncertainty of the interstellar gas density has always been an issue. To overcome this difficulty, we newly used a component decomposition of the 21-cm HI line emission and used the resulting gas maps in an analysis of gamma-ray data for the MBM 53, 54, and 55 molecular clouds and the Pegasus loop. First, we decomposed the ISM gas into several phases using detailed correlations with the HI line profiles from the HI4PI survey, the Planck dust-emission model, and the Fermi-LAT gamma-ray data. Then, we fitted the CR spectra directly measured at/near the Earth and the measured gamma-ray emissivity spectrum simultaneously. In the analysis, the Fermi-LAT data has played a crucial role as a robust tracer of the total ISM gas density and CR intensity. On the ISM side, we found the fraction of optical depth correction to the HI column density and CO-dark H2 to be nearly equal. On the CR side, we obtained a spectral break in the interstellar proton spectrum at about 7 GeV and found the gamma-ray emissivity normalization agrees with the AMS-02 spectrum within 10%. In this contribution, we will present the analysis/results based on the paper recently accepted (arXiv:2207.00214).

Speaker: Tsunefumi Mizuno

FermiSymp2022_MbmPegasus_2022-10_v1.0b.pdf

10:15 _

09:00 → 10:30 Parallel 12: GRBs and Fast Transients-II

09:00 Pulse fitting of short GRBs with known redshift detected by Fermi Gamma Ray Burst Monitor

Short gamma-ray bursts (SGRBs) are located at cosmological distances and their progenitors are compact binary mergers. These luminous events last for $T_{90}<2$ seconds. However, they are not the only events that last for that long. Magnetars, which are located in our galaxy or in nearby galaxies produce giant flares (MGFs). MGFs are short-hard energetic gamma-ray transients, similar to SGRBs that originate from highly magnetised neutron stars called Magnetars originating from star forming galaxies. Due to difficulties to easily distinguish these two transients, it is clear that the time interval that consists of 90% of the gamma-ray fluence is not sufficient to distinguish cosmological SGRBs from MGFs. In this study short GRBs with known redshift detected by Fermi Gamma ray burst monitor were selected for spectral studies in the energy range 10 keV - 40 MeV. The prominent peaks of the pulses were fit with the so-called Norris function. The function is a mathematical model that gives the rising and falling times of the pulses. This enables a better criteria to distinguish the two events by differentiating the rising and decaying times of SGRBs and MGF pulses.

Speaker: Ms Dimakatso Jeannett Maheso (University of Johannesburg)

DJ_Maheso_Fermi_Symposium_2022.pdf

09:15 Demystifying the Prompt Emission of Gamma Ray Bursts

Gamma Ray Bursts (GRBs) are the most powerful explosions in the universe, emitting more energy in a few seconds than our sun will emit in its entire lifetime. As a result, these explosions are excellent laboratories for exploring the interplay between matter and radiation in extreme environments. This interplay is integral to understanding astrophysical jets and the various compact objects that are thought to power GRBs. Recent advances in simulating the initial prompt emission of GRBs attempt to simulate this interplay between the jet properties and the resulting electromagnetic signature; this has resulted in various successes in reproducing observational aspects of GRBs. Here, we present the open source Monte Carlo Radiation Transfer (MCRaT) code. MCRaT propagates and Compton-scatters individual photons that have been injected into the collimated outflow in order to produce mock observed light curves, spectra, and polarization measurements from optical to gamma rays. These light curves and spectra allow us to compare our results to GRB observational data. We find excellent agreement between our mock observed GRBs and real GRB observations in terms of spectra and polarization measurements. Furthermore, we can understand the mock observations in terms of the jet structure and what real observations of GRBs can tell us about their jet structures. There are various improvements that can be made to MCRaT, but this code paves the way to connecting observed GRB radiation to the properties of the GRB jet in a way that was not previously possible.

Speaker: Tyler Parsotan

Parsotan_Fermi_10_symposium_pres_upload.pptx

09:30 Radiation-mediated shocks in gamma-ray bursts observed by Fermi

Radiation-mediated shocks (RMSs) below the photosphere may play an important role in the prompt emission of gamma-ray bursts (GRBs). However, fitting an RMS model to data has been infeasible due to the computational cost of simulating such shocks. We bridge the gap between theory and observation by creating an approximate but accurate model called the Kompaneets RMS approximation (KRA). In this talk, I present the first-ever fit of a prompt GRB spectrum with an RMS model by using Fermi data. Furthermore, we study the observational properties expected from RMSs in GRBs by generating synthetic KRA spectra. We find that the spectra often exhibit an additional break in X-rays, thus resembling a double broken power-law function with an exponential cutoff at high energies. When the synthetic KRA spectra are fitted with a cutoff power-law function, we find that the catalogue distribution of low-energy slopes are naturally reproduced.

Speaker: Dr Filip Samuelsson

Radiation-mediated shocks in photospheric GRB observations.pdf

09:45 Photons' scattering in a relativistic plasma with velocity shear: generation of high energy power-law spectra

High energy power law spectra is common to many astronomical objects. It is often assumed that such power laws are produced by energetic particles, obtaining a power law distribution by Fermi acceleration process.Here we present a novel mechanism of generating high-energy power-law shaped spectra by repeated photon scattering off velocity shear layers in relativistic jets. This mechanism does not invoke the existence of energetic particles. We show that for plausible parameters, the observed spectral shape of gamma-ray bursts is recovered. This mechanism is applicable to many different astronomical sources, and enables a unique tool to infer their inner structure.

Speaker: Asaf Pe'er

Photon_acc_Fermi.pdf

10:00 Implications of Cutoff observed in Fermi-LAT GRBs spectrum

The detections of photons above the pair-production threshold require the GRB outflow to be relativistic. The nature of the prompt emission (thermal or non-thermal), the jet composition, and the radius where the dissipation occurs in the outflow to produce the emission, are
uncertain. Spectral analyses of the LAT low-energy event (LLE) data of GRBs reveal a cut-off at $\lesssim$ 100 MeV. If we interpret this high-energy cutoff arising due to intrinsic opacity to pair production within the source, then it provides an estimate of the bulk Lorentz factor. Further, when supplemented by afterglow observations, this leads to constraints on the emission site of the prompt emission. These constraints, in conjunction with the detailed spectrum, decipher
the emission mechanism at work (thermal or non-thermal). Additionally, in the case of thermal mechanism, we can also constrain the efficiency of the prompt emission. From the analyses of joint Fermi-GBM, Fermi-LAT and afterglow data of GRB 190114C, following aforementioned framework, we conclude that the prompt emission is more consistent with produced via photospheric dissipation.

Speaker: Vikas Chand (Astrophysics Research Center of the Open University, Israel, Ra'anana)

VikasChandFS.key

VikasChandFS.pdf

VikasChandFS.pptx

10:15 Studying the viewing geometry of sGRBs and central engine using prompt emission

Prompt emission of short gamma-ray bursts (sGRBs) are analyzed using the model of the multi-color blackbody, which is interpreted as the emission from a non-dissipative photosphere with jet structure and viewing geometry inference. Nearly 69 % and 26 % of the sample is consistent with a multicolor blackbody and a pure blackbody model, respectively. Using this physical interpretation, a narrow jet core with a median of ~ 3 degrees and power-law index of 1.3 - 2.2 as decreasing Lorentz factor profile for the jet structure is deduced. Interestingly, based on the current LIGO sensitivity, the study predicts the rate of coincident detections of bright short GRBs with gravitational waves to be 0.19 - 2.87 events/yr. Another major quest in the field of GRB science is the nature of stellar remnants. Using the magnetar energy limit, 8 GRBs with black hole central engines are identified in 11 years of Fermi GRB sample (long and short both). The estimated masses of these bursts are found to range between 2 - 60 solar masses. A few of them are found to lie in the mass-gap region, suggesting that some of the lighter black holes in the Universe are formed via these catastrophic events.

Speaker: Vidushi Sharma

Vidushi_10thFSymp.pdf

10:30 → 11:00 Coffee Break

Posters

11:00 → 13:00 Plenary 7: Science Enabling Software

Convener: Jean Ballet

11:00 Anomaly Detection in Astronomical Data using Machine Learning

The next generation of telescopes such as the SKA and the Vera C. Rubin Observatory will produce enormous data sets, far too large for traditional analysis techniques. Machine learning has proven invaluable in handling large data volumes and automating many tasks traditionally done by human scientists. In this talk, I will discuss how machine learning for anomaly detection can help automate the process of locating unusual astronomical objects in large datasets thus enabling new cosmic discoveries. I will introduce Astronomaly, a general purpose framework for anomaly detection in astronomical data using active learning and overview some recent results.

Speaker: Dr Michelle Lochner (University of the Western Cape/ South African Radio Astronomy Observatory)

Backup-use link instead.pdf

Backup-use link instead.pptx

Google slides presentation - Lochner

11:30 Multi-wavelength data analysis with the threeML framework

With an increasing number of observatories making their data publicly available, we have truly reached the era of multi-wavelength astronomy. Combining gamma-ray data from multiple instruments as well as with measurements at other wavelengths is needed to unlock the data's full potential. However, lack of standardization as well as unique challenges of each instrument can make combining data from multiple instruments a challenging and time-consuming task.

ThreeML, the multi-mission maximum likelihood framework, is a python-based software package for multi-wavelength data analysis with a special focus on high-energy astronomy. Its flexible, plugin-based structure enables the inclusion of data from many different observatories in their diverse native formats without much additional effort by the user. ThreeML relies on astromodels, a flexible modeling framework, for the description of astronomical sources. Source modeling and data access are thus separate from likelihood optimization, and can be combined in a flexible manner. In addition to the (frequentist) maximum likelihood analysis, threeML also allows for Bayesian analysis via sampling of the posterior distribution. I will report on the current status of threeML and astromodels, and show some examples for joint likelihood fits using threeML.

Speaker: Nicola Omodei (Stanford University)

11:45 The Fermi Light Curve Repository

The Fermi Large Area Telescope Light Curve Repository (LCR) provides publication quality light curves on timescales of days, weeks, and months for over 1500 sources deemed variable in the 4FGL-DR2 catalog. The repository consists of light curves generated using a full likelihood analysis of the source and surrounding region, providing calibrated flux and photon index measurements for each time bin. The light curves hosted by the LCR cover the entire Fermi mission duration and are continually updated as soon as new data becomes available. The LCR is intended to serve as a resource to the time-domain and multi-messenger communities by allowing users to quickly search LAT data to identify correlated variability and flaring emission episodes from gamma-ray sources. We will provide an overview of the analysis employed by the LCR and the associated data access portal, and discuss the tools developed to allow users to easily download and use the LCR data.

Speaker: Dan Kocevski

12:00 Identifying multiwavelength counterparts to astrophysical neutrino events

At production, high-energy neutrinos originating in astrophysical sources should be accompanied by gamma-rays. Depending on the properties of the emission environment and the distance of the source to Earth these gamma rays may be observed directly, or through the detection of lower energy photons that result from the interaction of these gamma rays with intervening radiation fields. We here present an update on an automated tool that aims to identify multiwavelength counterparts to astrophysical neutrinos events. The main goal of this tool is to enable prompt follow-ups by ground- and space-based observatories to help pinpoint the neutrino source.

Speaker: Dr Marcos Santander (University of Alabama)

santander_fermisymp22.pdf

12:15 General Coordinates Network (GCN): NASA’s Next Generation Time-Domain and Multimessenger Astronomy Alert System

The Gamma-ray Coordinates Network (GCN) is a public collaboration platform run by NASA for the astronomy research community to share alerts and rapid communications about high-energy, multimessenger, and transient phenomena. Over the past 30 years, GCN has helped enable many seminal advances by disseminating observations, quantitative near-term predictions, requests for follow-up observations, and observing plans. GCN distributes alerts between space- and ground-based observatories, physics experiments, and thousands of astronomers around the world. With new transient instruments from across the electromagnetic spectrum and multimessenger facilities, this coordination effort is more important and complex than ever. We introduce the General Coordinates Network, the modern evolution of GCN built on modern, open-source, reliable, and secure alert distribution technologies, and deployed in the cloud. The new GCN is based on Apache Kafka, the same alert streaming technology that has been selected by the Vera C. Rubin observatory. In this poster, we will present the status and design of the new GCN, a tutorial on how to stream alerts, and a vision of its growth as a community resource in the future.

Speaker: Dr Judith Racusin (NASA/GSFC)

GCN_ General Coordinates Network.pdf

12:30 Astro-COLIBRI

Astro-COLIBRI is a novel platform that evaluates alerts of transient observations in real time, filters them by user-specified criteria, and puts them into their multiwavelength and multimessenger context. Through fast generation of an overview of persistent sources, as well as transient events in the relevant phase space, Astro-COLIBRI contributes to an enhanced discovery potential of both serendipitous and follow-up observations of the transient sky.

In this contribution, we'll present the key features of Astro-COLIBRI. We'll outline the architecture, summarize the used data resources and provide examples for applications and use cases. Focussing on the high-energy domain, we'll for example showcase the search for high-energy gamma-ray counterparts to high-energy neutrinos and highlight the connections with Fermi-LAT platforms like FAVA and the LCR.

Speaker: Patrick Reichherzer

Astro-COLIBRI_10thFermi_Symposium.pdf

12:45 easyFermi: a graphical interface for performing Fermi-LAT data analyses

Since its launch in 2008, the Fermi Large Area Telescope (LAT) allowed us to investigate the extremely energetic side of the Universe with unprecedented sensitivity and resolution. The tools available for analyzing Fermi-LAT data are the Fermitools and Fermipy, both of which can be scripted in Python and run via command lines in a terminal or in web-based interactive computing platforms. In this talk, we present easyFermi, an open-source user-friendly graphical interface for performing basic to intermediate analyses of Fermi-LAT data in the framework of Fermipy. With easyFermi, the user can quickly measure the γ-ray flux and photon index, build spectral energy distributions, light curves, test statistic maps, test for extended emission and even relocalize the coordinates of γ-ray sources. The tutorials for easyFermi are available on YouTube and GitHub, allowing the user to learn how to use Fermi-LAT data in about 10 min.

Speaker: Raniere Menezes (Universidade de São Paulo)

Fermi Symp 2022 V3.pdf

13:00 → 14:00 Lunch

14:00 → 16:00 Plenary 8: Future Missions

Convener: Judy Racusin (NASA/GSFC)

14:00 Future Science enabled by COSI: the Compton Spectrometer and Imager

The Compton Spectrometer and Imager (COSI) is a soft gamma-ray telescope that was recently selected to be NASA’s next SMEX mission with a launch in 2026. COSI has a unique combination of excellent spectral resolution and large instantaneous field of view (>25%-sky). The mission is designed to uncover the source of Galactic positrons, image diffuse emission from stellar nucleosynthesis, and perform polarization studies of gamma-ray bursts and compact objects. With unprecedented sensitivity in the MeV range, COSI is expected to provide advances in the time-domain and multimessenger astrophysics and reveal new classes of gamma-ray sources. In this presentation I will give an overview of the future studies enabled by COSI, emphasizing possible synergies and complementarities with Fermi’s science.

Speaker: Michela Negro

COSI_FermiSymposium.pdf

14:30 The Moon Burst Energetics All-sky Monitor (MoonBEAM)

MoonBEAM is a SmallSat concept placed in cislunar orbit developed to study the progenitors and multimessenger/multiwavelength signals of transient relativistic jets and outflows and determine the conditions that lead to the launching of a transient relativistic jet. The distinguishing advantage of MoonBEAM is the instantaneous all-sky coverage, maximizing the gamma-ray transients observations and providing upper limits for non-detections. Gamma-ray observatories in low Earth orbit are not able to survey the entire sky at a given time due to Earth blockage as well as detector downtime from the high particle activity in the South Atlantic Anomaly region. The long baseline provided from a cislunar orbit, allows MoonBEAM to constrain the localization annulus when combined with a gamma-ray instrument in low Earth orbit utilizing the timing triangulation technique. Improving the localization precision of a gamma-ray burst aids the gravitational wave follow-up community in reducing the region needed to be searched to locate and identify the afterglow and kilanova emission. Furthermore, by providing a different vantage point for a gamma-ray detection, MoonBEAM can help extend the gravitational wave detection horizon by increasing the confidence of a simultaneous marginal gravitational wave signal. Through the all-sky coverage, MoonBEAM will also provide insight into the conditions that lead to a successful relativistic jet, instead of a shock breakout event, or a completely failed jet in the case of core collapse supernovae.

Speaker: Cori Fletcher

cfletcher_moonbeam.pptx

14:45 Polarimetry of gamma rays converting to e+e- pairs: performance of silicon strip detectors-based telescopes

The polarimetry of gamma rays converting to an e+e- pair would open a new window on the high-energy sky with, among other things, providing insight into the radiation mechanism in young pulsars (curvature or synchrotron) or deciphering the composition of the gamma-ray emitting jets in blazars (leptonic or lepto-hadronic).

The performance of polarimeters based on homogeneous active targets (gas detectors (MeV, HARPO) or emulsions (GeV, GRAINE)) has been studied both with simulation and by the analysis of data collected with telescope prototypes on linearly-polarized gamma-ray beams, and found to be excellent, but the present (Fermi-LAT, AGILE) and project (AMEGO, ASTROGAM) gamma-ray missions are using active targets based on silicon strip detectors (SSD). After past attempts to demonstrate a non-zero effective polarization asymmetry with SSDs failed, be it only with simulated data, published sensitivity estimations had to be obtained from an assumed value of the effective polarization asymmetry.

I will present a characterization of the potential of SSD-based active targets for polarimetry with gamma ray conversions to pairs, and the development of various methods to improve on the sensitivity. These results were obtained using data simulated with my home-made, exact, five-dimensional, event generator and a dedicated event-reconstruction method. This work could pave the way to providing the polarimetry of the brightest gamma-ray sources of the sky from the decade of data collected by the Fermi-LAT and by AGILE, and to guiding the design of future missions.

Speaker: Denis Robert Leon Bernard (Centre National de la Recherche Scientifique (FR))

FermiSymposium2022_DBernard.pdf

15:00 THE ASTRI MINI-ARRAY AT THE OBSERVATORIO DEL TEIDE

The ASTRI Mini-Array is a gamma-ray experiment led by INAF with the partnership of
the Instituto de Astrofisica de Canarias, Fundacion Galileo Galilei, Universities of Sao Paulo,
North-West University S.A. It is being implemented at the Observatorio del Teide in Tenerife. The ASTRI Mini-Array will encompass nine identical Cherenkov dual-mirror aplanatic telescopes positioned at a minimum distance from each-other of about 250 m. Thanks to their unprecedented field-of-view (10.5 deg), the Mini-Array will allow us to observe the gamma-ray sky from a few up to few hundreds TeVs with high sensitivity and enhanced angular resolution. The curved focal camera is covered with SiPM sensors and it is equipped with a fast front-end electronics. The control SW will allow us to operate remotely the Mini-Array, while a dedicated off-site DataCenter in Italy will process the data collected every night. The ASTRI Mini-Array represents a key instrument to perform very soon a ground breaking achievement in the field of extreme gamma rays. In this contribution, the project status and the expected performance of the ASTRI Mini-Array will be presented.

Speaker: Prof. Patrizia Caraveo (INAF-IASF Milano)

MAstatus-Caraveo-Fermi Symp.pdf

15:15 BurstCube: A CubeSat for Gamma-Ray Counterparts to Gravitational Waves

BurstCube is a 6U (10 x 20 x 30 cm) CubeSat launching in 2023 that is designed to expand our view of the gamma-ray sky, complementary to Fermi-GBM and Swift-BAT. It will detect gamma-ray bursts and other short-duration transients, including those that could be coincident with gravitational wave detections of neutron star mergers. It is composed of four 9-cm diameter CsI scintillator crystals coupled to arrays of silicon photomultipliers. They are pointed 45 degrees apart and will observe the energy band from 50keV to 1MeV. I will describe the mission overview, the status of development, and plans for on-orbit operations, including some novel features for a CubeSat, such as requested data downloads and usage of the NASA Tracking and Data Relay Satellite System (TDRSS)

Speaker: Pi Nuessle (NASA Goddard Space Flight Center)

BurstCube A CubeSat for Gravitational Wave Counterparts.pptx

15:30 AMEGO-X Mission Overview

Gamma-ray and multimessenger astrophysics are frontiers for discovery and uniquely provide access to the extreme processes that sculpt the universe. Multimessenger astrophysics is one of the most exciting and rapidly advancing fields of science. As a priority theme of the Astro2020 Decadal Survey report: New Messengers New Physics, this science is poised to revolutionize our understanding of the extreme universe. Data from NASA’s Fermi mission demonstrated that the extreme processes that produce gravitational waves and accelerate neutrinos and cosmic rays also produce gamma rays. In other words, multimessenger sources are gamma-ray sources. Now is the time to develop a powerful mission to fill these critical capability gaps revealed by Fermi and fully capitalize on this exciting new era of multimessenger astrophysics.

The All-sky Medium Energy Gamma-ray Observatory eXplorer (AMEGO-X) will observe nearly the entire sky every two orbits, building up a sensitive all-sky map of gamma-ray sources and emission. It will also access >50% (<10 MeV) and >20% (>10 MeV) of the sky instantaneously, maximizing transient detections and rapid alerts, openly distributed to the astrophysics communities. As a result, AMEGO-X will deliver breakthrough discoveries for a MIDEX class in areas highlighted as the highest scientific priority for Explorer-scale missions in the Astro2020 Decadal Survey Report: gravitational waves, multimessenger astrophysics and time-domain astronomy. This talk presents an overview of the science, instrument, and mission that was submitted in the recent 2021 NASA MIDEX Announcement of Opportunity.

Speaker: Regina Caputo (NASA/GSFC)

Caputo_AMEGO-X_Mission_Overview.pdf

16:00 → 16:30 Coffee Break

16:30 → 17:00 Plenary 9: Future Missions

Convener: Soebur Razzaque

16:30 The Cherenkov Telescope Array: Status and Perspectives

The Cherenkov Telescope Array will be five to ten times more sensitive with respect to the current generation Imaging Atmospheric Cherenkov Telescopes and will have an unprecedented accuracy in its detection of very-high-energy gamma rays in the energy range from 20 GeV to 300 TeV.
CTA is designed to detect gamma rays over a larger area with dozens of telescopes located on the Canary island of La Palma and at Paranal in the Atacama desert in Chile, in the northern and southern hemispheres respectively. Together, the northern and southern CTA arrays will constitute the CTA Observatory (CTAO), which will be the first ground-based gamma-ray observatory open to the worldwide astronomical and particle physics communities as a resource for data from unique, high-energy astronomical observations.
The talk will present the current status of development of the telescopes, of the Observatory and the perspectives for its scientific observations.

Speaker: Francesco Longo

CTA_FermiSymposium_Sep2022_v2.pdf

16:45 The Southern Wide field-of-view Gamma-ray Observatory

Particle-detector arrays at high altitude proved to be very effective instruments for performing surveys on a daily basis of the very-high-energy gamma-ray sky. In the northern hemisphere, the HAWC and LHAASO gamma-ray observatories recently conducted an all-sky survey that provided significant improvements to our knowledge about Very High Energy TeV gamma-ray sources. In this contribution, we will present an overview of the international effort to realize a next-generation gamma-ray survey observatory in the southern hemisphere, The Southern Wide field-of-view Gamma-ray Observatory (SWGO). We will discuss the unique science case for this observatory with particular emphasis on the multi-messenger and multi-wavelength connections.

Speaker: Francesco Longo

SWGO_FermiSymposium2022_FrancescoLongo_v2.pdf

17:00 → 17:30 Closing

Convener: Soebur Razzaque

17:00 Equity and diversity in science

Speaker: Debra Meyer (University of Johannesburg)

17:15 Closing remarks

Speaker: Soebur Razzaque