-
Soebur Razzaque (University of Johannesburg)12/04/2021, 15:00
-
Markus Boettcher (North-West University)12/04/2021, 15:10
-
Judith Racusin12/04/2021, 15:15
-
Judith Racusin12/04/2021, 15:30
-
Igor Andreoni12/04/2021, 16:00
-
Michelle Hui12/04/2021, 16:25
The Fermi Gamma-ray Burst Monitor (GBM) is an all-sky monitoring instrument designed to detect the prompt emission from a gamma-ray burst (GRB) and provide near-real time locations for follow-up observations. Over the past 11 years of operation, the GBM has detected over 240 gamma-ray bursts per year and provided timely community notices with localization to few-degree accuracy such as GRB...
Go to contribution page -
Lara Nava12/04/2021, 17:05
High energy radiation (0.1-100 GeV) from GRBs is regularly detected by Fermi-LAT in a sizable fraction of bright GRBs. The presence of emission at even higher energies instead has been discovered only recently, thanks to detections by the MAGIC and H.E.S.S. Cherenkov telescopes. These detections have shown that very high energy (VHE) emission up to at least 1 TeV can indeed be produced in...
Go to contribution page -
Yusuke Suda12/04/2021, 17:30
Gamma-ray bursts (GRBs) are the most luminous explosions in the Universe. Their nature has been well studied using enormous amounts of GRB data in a broad range of the electromagnetic spectrum, from radio frequencies up to GeV energies. However, several theoretical studies had been predicting TeV emission as well, but it could not be detected for a long time.
Go to contribution page
The MAGIC collaboration had been... -
Dr Elisabetta Bissaldi12/04/2021, 17:45
Current Imaging Atmospheric Cherenkov Telescopes (IACTs) have only recently begun to detect very-high energy emission (VHE; >100 GeV) from Gamma-Ray Bursts (GRBs). Here we report on the observations of the extremely bright and rather nearby GRB 180720B by the High Energy Stereoscopic System (H.E.S.S.), leading to its detection in the 100–440 GeV energy range. This detection was achieved over...
Go to contribution page -
Tanita Ramburuth-Hurt12/04/2021, 18:00
Diffuse radio emission in the form of the "WMAP/Planck haze" has been established to exist within 1-2 kpc of the center of the Milky Way. If this haze is a product of dark matter annihilations, it should be detectable in spiral galaxies that are similar to the Milky Way. In this project, we use the cosmic ray propagation software, Galprop, to predict the flux, morphology and spectrum of a dark...
Go to contribution page -
Alexei Pozanenko12/04/2021, 18:00
Observations of the gravitational-wave event GW190425 registered by the LIGO/Virgo detectors with the Anti-Coincidence Shield (ACS) of the gamma-ray spectrometer SPI aboard the INTEGRAL observatory are presented. This is only the second event of binary neutron star merging type (> 99% probability) after GW170817. A weak gamma-ray burst, GRB190425, consisting of two pulses in 0.5 and 5.9 s...
Go to contribution page -
Maria Chernyakova (DCU)12/04/2021, 18:00
Gamma-ray binaries are a relatively new subclass of High Mass X-ray binaries visible from radio up to very high (TeV) energies. At the moment only a handful such sources (less than 10) are regularly observed at TeV and GeV energies. Only in two of these systems, PSR B1259-63 and PSR J2032+4127 we are sure on the nature of the compact objects, as these systems are wide enough to detect...
Go to contribution page -
Barbara Patricelli12/04/2021, 18:15
The joint observation of GW170817 and GRB170817A proved that binary neutron star (BNS) mergers are progenitors of short Gamma-ray Bursts (SGRB): this established a direct link between the still unsettled SGRB central engine and the outcome of BNS mergers, whose nature depends on the equation of state (EOS) and on the masses of the NSs. We propose a novel method to probe the central engine of...
Go to contribution page -
Brian van Soelen12/04/2021, 18:15
Gamma-ray binaries are a rare class of binary system which produce non-thermal emission which peaks in the gamma-ray regime and so far, only seven sources have been firmly identified. These systems consist of a O/B type star and either a neutron star or a black hole compact object. Establishing the orbital parameters of gamma-ray binaries is a crucial requirement for modelling the emission...
Go to contribution page -
Christopher Michael Karwin12/04/2021, 18:15
The upper limits from the Milky Way (MW) dwarf spheroidal galaxies remain one of the most important constraints on dark matter (DM) annihilation, and specifically, they are crucial for DM interpretations of the Galactic center excess. The last detailed analysis by the Fermi-LAT Collaboration dedicated to studying the dwarfs was published in 2017, using roughly 6 years of data. Now, with over...
Go to contribution page -
Viviana Gammaldi (SISSA)12/04/2021, 18:30
Dwarf irregular (dIrr) galaxies have been shown to be dark matter (DM) dominated systems and proposed as interesting targets for the indirect search for DM with gamma rays. In this work, we analyze 11 years of Fermi-LAT data corresponding to the sky regions of 7dIrrs at a distance of less than ~1 Mpc. Due to the current uncertainty in the DM density distribution in these objects, we consider...
Go to contribution page -
Cecilia Chirenti12/04/2021, 18:30
It is known from theoretical models and the observation of GW170817 that short gamma ray bursts (SGRBs) can be emitted by the merger of two neutron stars. The outcome of this merger may produce a short-lived (~ 100 ms) hypermassive neutron star (HMNS) before collapsing to a black hole. If the SGRB is emitted during the HMNS phase, it may be modulated by oscillations of the HMNS, with expected...
Go to contribution page -
Andrzej Zdziarski12/04/2021, 18:30
The high-mass accreting binary Cyg X-3 is distinctly different from low-mass X-ray binaries (LMXBs) in having radio and gamma-ray emitting jets in its soft spectral state. Furthermore, those jets are much brighter in both radio and gamma-rays than those in the hard state of this object. Analysis of those emissions (Zdziarski et al. 2018) yields the location and the profiles of the orbital...
Go to contribution page -
Javier Coronado-Blázquez (IFT UAM-CSIC)12/04/2021, 18:45
ΛCDM predicts the existence of dark matter (DM) subhalos, most of them not massive enough to retain gas (i.e., baryons) and become visible. If DM is composed of Weakly Interacting Massive Particles (WIMPs), we expect them to annihilate in subhalos, producing gamma rays which can be detected with the Large Area Telescope (LAT) onboard the Fermi satellite, and appearing as unidentified sources...
Go to contribution page -
Gor Oganesyan12/04/2021, 18:45
Being discovered more than 40 years ago, gamma-ray bursts (GRBs) remain one of the mysterious astrophysical objects. In fact, the physics of relativistic jets formation, their composition, dissipation processes are still some of the biggest unknown in GRBs. The inability to establish the radiative processes shaping the observed prompt emission spectra does not allow us to make a big step...
Go to contribution page -
Jian Li (Deutsches Elektronen-Synchrotron DESY)12/04/2021, 18:45
Microquasars, the local siblings of extragalactic quasars, are binary systems comprising a compact object and a companion star. By accreting matter from their companions, microquasars launch powerful winds and jets, influencing the interstellar environment around them. Steady gamma-ray emission is expected to rise from their central objects, or from interactions between their outflows and the...
Go to contribution page -
Mattia Di Mauro12/04/2021, 19:00
The excess of gamma rays in the data measured by the Fermi Large Area Telescope from the Galactic center region is one of the most intriguing mysteries in Astroparticle Physics. This Galactic center excess (GCE), has been measured with respect to different interstellar emission models, source catalogs, data selections and techniques. Although several proposed interpretations have appeared in...
Go to contribution page -
Iurii Sushch (Deutsches Elektronen-Synchrotron DESY)12/04/2021, 19:00
Gamma-ray binaries are a small but growing class of sources which comprises of binary systems where the spectral energy distribution peaks above 1 MeV. Gamma-ray photons emitted in binary systems are subject to gamma-gamma absorption as they travel through a photon field created by a massive star. Moreover, gamma-gamma absorption might be the main reason for the characteristic decrease of the...
Go to contribution page -
Maria Edvige Ravasio12/04/2021, 19:00
At last, after more than 40 years from their discovery, the long-lasting tension between predictions and observations of GRBs spectra could be solved. We realized that the observed spectra can be produced by the synchrotron process from a distribution of electrons truncated at low energies. This low energy cut-off demands that electrons do not completely cool. Evidence for incomplete cooling...
Go to contribution page -
Guillem Martí-Devesa12/04/2021, 19:15
Unlike in supernova remnants or pulsar-wind nebulae, the characterization of high-energy and very-high-energy emission in binary systems allows the study of particle acceleration in shocks under periodically varying conditions. However, less than ten massive stars with non-accreting neutron star companions have been found to radiate most of their electromagnetic emission in gamma-rays....
Go to contribution page -
Davide Serini (Universita e INFN, Bari (IT))12/04/2021, 19:15
Dark matter particles in the Galactic halo could interact with the nuclei in the solar environment and be then gravitationally trapped by the Sun. In this framework, the overdensity of dark matter particles in the Sun core or in external orbits will result in annihilations of these particles producing gamma rays outside the Sun, either directly or via long-lived intermediate states.
We...
Go to contribution page -
Francesco Longo12/04/2021, 19:15
Very high energy astrophysical sources show flaring and transient behaviour on different timescales, from fraction of seconds to years. These transient sources are usually observed and monitored over the whole electromagnetic spectrum. This contribution will outline the very high energy (VHE, $E>100$ GeV) transient search program operated by the MAGIC telescopes. In this context, Imaging...
Go to contribution page -
Pablo Saz Parkinson (The University of Hong Kong)13/04/2021, 07:00
The Fermi LAT Fourth Source Catalog (4FGL) contains over 5000 gamma-ray sources detected using 8 years of LAT data. Among these sources, over 3000 are associated with known blazars, 239 are associated with pulsars, and over 1300 are classified as 'unassociated' sources, meaning they have no known plausible counterpart at any other wavelength. Following on our previous work on the 3FGL Catalog...
Go to contribution page -
Andrea Gokus13/04/2021, 07:00
While blazars are abundant in the gamma-ray sky, there is only a handful of narrow-line Seyfert 1 galaxies that Fermi/LAT detected in more than 10 years of observation. Flares from this elusive source class are among the rarest events that Fermi has seen so far.
Go to contribution page
One of them is the radio- and gamma-ray loud source PKS 2004-447. It exhibits blazar-like features, i.e., a flat featureless X-ray... -
Nomthendeleko Motha13/04/2021, 07:03
The extragalactic radio background in the universe is mainly due to emission from the radio galaxies and normal galaxies. This emission is synchrotron radiation by relativistic electrons gyrating in the magnetic field of the galaxies. Synchrotron self-absorption and free-free absorptions by hot ionised gas in the interstellar medium play an important role to modify radio emission. In this...
Go to contribution page -
Laenita Oberholzer13/04/2021, 07:06
On the 28th of January, an orphan very-high-energy γ-ray flare from 3C279
Go to contribution page
was detected, not accompanied by flaring in the adjacent GeV gamma-ray
regime. Orphan flares have to be caused by different processes than normal
γ-ray flares. Specifically, the Hadronic Synchrotron Mirror Model has been
proposed to provide a consistent explanation of this flare. The expected tar-
get photon... -
Isabella Mereu13/04/2021, 07:07
Gamma-ray catalogs produced with data of the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope typically integrate years of exposure. Since Active Galactic Nuclei (AGNs) are characterized by strong and fast variability, their emission is diluted by long-time data integration. Transient sources can be more easily detected over short time scales. In order to search for...
Go to contribution page -
Hannes Thiersen13/04/2021, 07:09
Most research on blazar variability focuses on individual flares to explain acceleration
Go to contribution page
and radiation mechanisms and improve on current models. These short-time events
(being minutes, hours, or days) might not be representative of the underlying mecha-
nisms causing small-amplitude variability and/or continuous emission which is present
most of the time. We will therefore investigate... -
Zacharias Michael13/04/2021, 07:12
The FSRQ CTA 102 (z=1.032) has been tremendously active over the last few years. During its peak activity lasting several months in late 2016 and early 2017, the gamma-ray and optical fluxes rose by up to a factor 100 above the quiescence level. We have interpreted the peak activity as the ablation of a gas cloud by the relativistic jet, which can nicely account for the months-long lightcurve...
Go to contribution page -
Naomi Tsuji13/04/2021, 07:14
We report the results of cross-match between the hard X-ray and GeV gamma-ray catalogs, by making use of the latest 105-month Swift/BAT and 10-yr Fermi/LAT catalogs, respectively. We found 181 matched sources in total, which include 36 of false-match, unidentified, and ambiguous sources. The firmly matched sources consist of blazars (> 60%), pulsars and pulsar wind nebulae (∼10%), radio...
Go to contribution page -
Natalia Zywucka13/04/2021, 07:15
We present the results of a preliminary investigation of a potential association of a blazar
Go to contribution page
candidate behind the Large Magellanic Cloud (LMC) and a gamma-ray transient object.
The hint of flaring activity appeared at the position (RA,dec)∼(86.60 deg,-69.02 deg), while
the J0545-6846 blazar candidate is located at (RA,dec)=(86.47 deg,-68.77 deg). J0545-6846 is characterised by a... -
Yasushi Fukazawa13/04/2021, 07:18
FSRQs are important to study cosmic evolution of AGN jet and also interesting how they contribute to the cosmic MeV gamma-ray background. Past studies with hard X-ray (Swift/BAT 22 month catalog) and GeV gamma-ray (Fermi/LAT) reported the X-ray and gamma-ray luminosity function, but predicts a different evolution between X-ray and GeV gamma-ray. Here we used the Swift/BAT 105 month catalog to...
Go to contribution page -
Mithun Randu13/04/2021, 07:21
An active galactic nucleus with a relativistic jet pointing within 10o of the line of the sight of the earth is known as a Blazar. Normally a Blazar has two relativistic jets. These jets are linear features instigating very close to the super massive black hole (SMBH) at the center of an Active Galactic Nucleus (AGN). A broad region of energies consist in these jets from radio rays to gamma...
Go to contribution page -
Elena Orlando13/04/2021, 07:21
The Fermi Large Area Telescope (LAT) has been detecting hundreds of Galactic sources, most of which are pulsars. Many Galactic sources are still undetected or unresolved due to their low flux, below the Fermi LAT sensitivity, or because of foreground and source confusion. Moreover, among the many unassociated sources, which are one third of the detected sources, a large amount may have...
Go to contribution page -
Jacobus van den Berg13/04/2021, 07:24
We test different physically motivated models for the spectral shape of the gamma-ray emission in a sample of 128 blazars with known redshifts detected by Fermi-LAT at energies above 50 GeV. The first nine years of LAT data in the energy range from 300 MeV to 2 TeV are analyzed in order to extend the spectral energy coverage of the 2FHL blazars in our sample. We compare these spectral data to...
Go to contribution page -
Marco Ajello13/04/2021, 07:27
Massive black holes at the centers of galaxies can launch powerful wide-angle winds, which if sustained over time can unbind the gas from the stellar bulges of galaxies. Propagating through the galaxy, the wind should interact with the interstellar medium creating a strong shock, similar to those observed in supernovae explosions, which is able to accelerate charged particles to high...
Go to contribution page -
Luca Giunti13/04/2021, 07:28
The identification of active PeVatrons, hadronic particle accelerators reaching the knee (at the energy of few PeV), is crucial to understand the origin of cosmic rays in the Galaxy. In this context, we report on new H.E.S.S. observations of the PeVatron candidate HESSJ1702-420, close to the source 2FHL J1703.4-4145, that have revealed the presence of gamma-rays up to 100 TeV at 5 sigma...
Go to contribution page -
Melissa Hallum13/04/2021, 07:30
The quasar 1156+295 (4C 29.45, Ton599) underwent a dramatic nonthermal outburst in late 2017, with detection at energies > 100 GeV. The outburst was essentially simultaneous at gamma-ray and optical bands, indicating co-spatiality of the emission regions. We present multi-epoch optical spectra of 1156+295 obtained with the 4.3 m Lowell Discovery Telescope at various times, including the...
Go to contribution page -
178. Multiwavelength monitoring of gravitationally lensed blazar QSO B0218+357 between 2016 and 2020Francesco Longo13/04/2021, 07:33
QSO B0218+357 is currently the only gravitationally lensed source from which both high-energy (HE, >~100 MeV) and very-high-energy (VHE,>~100GeV) gamma-ray emission has been detected.
We report the Fermi/LAT and multiwavelength monitoring observations of this source in radio interferometry, optical and X-rays performed between 2016 and 2020. During the monitoring, individual flares in the...
Go to contribution page -
Michael Sarkis13/04/2021, 07:35
Recent studies of the effects on the Earth’s atmosphere by astrophysical sources, such as nearby gamma-ray bursts or supernovae, have shown that these events could lead to severe changes in atmospheric composition. Depletion of ozone, the most notable of these changes, is extremely dangerous to living organisms as any decrease in ozone levels leads to an increase in the irradiance of harmful...
Go to contribution page -
Alex McDaniel13/04/2021, 07:36
Many star-forming galaxies and those hosting active galactic nuclei (AGN) show evidence of massive outflows of material in a variety of phases including ionized, neutral atomic, and molecular outflows. Molecular outflows in particular have been the focus of recent interest as they may be responsible for removing gas from the galaxy, thereby suppressing star formation. As the material is...
Go to contribution page -
Zhiyuan Pei13/04/2021, 07:39
In this talk, we will present a two-component model of the γ-ray emission which assumes that the total γ-ray output of blazars consists of relativistically beamed and unbeamed components. 584 Fermi/LAT-blazars are listed in our compiled catalogue. This idea leverages the correlation between the radio core-dominance parameter and the γ-ray beaming factor. We firstly propose a so-called "γ-ray...
Go to contribution page -
Geoff Beck13/04/2021, 07:42
Gamma-ray probes have historically been a gold-standard in indirect dark matter detection due to their smaller set of complicating factors and generally lower backgrounds. However, they are most optimally sensitive to the traditional supersymmetric WIMP annihilation channels and leptophilic channels (particularly for larger masses) are much harder to probe effectively in this manner. However,...
Go to contribution page -
Giacomo Principe13/04/2021, 07:42
According to radiative models, radio galaxies are predicted to produce gamma rays since the first stages of their evolution. The study of the high-energy emission from young radio sources is crucial for providing information on the most energetic processes associated with these sources, the actual region responsible for this emission, as well as the structure of the newly born radio jets....
Go to contribution page -
Rozeena Ebrahim13/04/2021, 07:45
The Circinus galaxy is a composite starburst/Seyfert galaxy which exhibits radio lobes inflated by kpc scale outflows along its minor axis. Its proximity (4 Mpc) makes it a unique target to study the physical nature of these outflows. We investigate if they originate from nuclear star formation activity or if they are jets from an active galactic core. The MeerKAT radio observations allow us...
Go to contribution page -
Bindu Rani13/04/2021, 07:48
Magnetic reconnection - relinking of magnetic field lines - has been proposed as a possible mechanism to power the high-energy flares in gamma-ray bright Active Galactic Nuclei but has not been confirmed via observations. Our study found observational evidence of magnetic reconnection generated gamma-ray flares in a radio galaxy, 3C 84. In a sequence of radio images, the radio-emitting region...
Go to contribution page -
Alejandra Aguirre-Santaella13/04/2021, 07:49
TeV DM candidates are gradually earning more and more attention within the community. Among others, extra-dimensional brane-world models may produce thermal DM candidates with masses up to 100 TeV, which could be detected with the next generation of very-high-energy gamma-ray observatories such as the Cherenkov Telescope Array (CTA).
Go to contribution page
In this work, we study the sensitivity of CTA to branon DM... -
Joseph Omojola13/04/2021, 07:51
Phenomenological spectral analysis of S5 1803+784 was done in both the high state and the low state using leptonic jet models. The jet energetic and spectral properties using single zone synchrotron-self Compton (SSC) and SSC with external photons (SSC+EC) jet models are presented. S5 1803+784 is a low synchrotron peak (LSP) blazar with the characteristics weak emission lines
Go to contribution page
(EW < 5A ).... -
JP Marais13/04/2021, 07:54
The Fermi-LAT has detected more than 5000 gamma-ray sources which show emission above 50 MeV of which 58 per cent belong to the blazar class. However, the Fourth Fermi-LAT catalogue (4FGL) lists 1312 of these as blazar candidates of uncertain type (BCU). Increasing the number of classified Fermi-LAT sources is important for improving our understanding of extra-galactic gamma-ray sources and...
Go to contribution page -
Jeremy Hare13/04/2021, 07:56
The release of the Fermi-LAT 4FGL catalog includes over 1,000 unidentified Fermi-LAT sources (roughly 25% of sources). One of the most successful ways to uncover their counterparts are through X-ray observations. Over their ~20 year lifetimes XMM-Newton and Chandra have observed a large number of Galactic fields, many of which contain unidentified Galactic Fermi-LAT sources. Often these fields...
Go to contribution page -
Graziano Chiaro13/04/2021, 07:57
Radio-loud sources with blazar-like properties, but having a jet that does not directly point in the direction of the observer are among the most interesting classes of gamma-ray emitters. These sources are known as Misaligned Active Galactic Nuclei (MAGN). We searched for new MAGN candidates among the remaining blazars of uncertain type detected by the Fermi Large Area Telescope (LAT) using a...
Go to contribution page -
Saikat Das13/04/2021, 08:00
We explain the observed multiwavelength photon spectrum of some high energy BL Lac objects, using a lepto-hadronic model. The one-zone leptonic emission is employed to fit the synchrotron peak. Subsequently, the SSC spectrum is calculated, such that it extends up to the highest energy possible for the jet parameters considered. The data points beyond this and also in the entire VHE range (E>30...
Go to contribution page -
Brandon Bisschoff13/04/2021, 08:03
Galaxies and galaxy clusters are separated by large distances of nearly empty
Go to contribution page
space called the intergalactic space. In these large, nearly empty regions a weak magnetic field of strength < 10 nG is present that is predicted to be of primordial (early universe) origin. This is called the intergalactic magnetic field (IGMF) and knowledge about its strength, coherence length, origin etc. is... -
Werner Collmar13/04/2021, 15:00
The COMPTEL experiment aboard the Compton Gamma-Ray Observatory (CGRO) surveyed the MeV sky (0.75 - 30 MeV) almost uninterruptedly for more than 9 years between April 1991 and June 2000, thereby providing a first all-sky view in the MeV band. Now, about 20 years after the de-orbit of CGRO, COMPTEL data analyses are being still pursued. New imaging techniques allow updated all-sky images...
Go to contribution page -
Gudlaugur Johannesson13/04/2021, 15:00
A handedness in the arrival directions of high-energy photons from outside our Galaxy can be related back to the helicity of the inter-galactic magnetic field. Previous estimates by Tashiro et al. (2014) showed a hint of a signal present in the photons observed by the Fermi Large Area Telescope (LAT). An update on the measurement of handedness in the arrival direction of photons observed by...
Go to contribution page -
Daniela Dorner13/04/2021, 15:00
To understand extremely variable sources like Active Galactic Nuclei,
Go to contribution page
unbiased monitoring is of great importance. Often multi-wavelength
observations are triggered by flaring activities of the sources which
biases the overall data sample towards higher fluxes. Studying flux
correlations between different wavelengths or flux distributions, an
unbiased data sample is crucial. In the GeV... -
Giulio Lucchetta13/04/2021, 15:15
Despite the great success achieved both by X-ray and gamma-ray observatories in the past two decades, the region of the electromagnetic spectrum around 1 MeV remains largely unexplored. COMPTEL, on board CGRO (1991-2000), was the last telescope to observe this region, with a modest sensitivity. New gamma-ray observatories, like AMEGO and e-Astrogam, have been proposed for the future, in order...
Go to contribution page -
Marcello Giroletti13/04/2021, 15:15
While still outnumbered by sources with a small viewing angle, i.e. blazars, the population of misaligned active galactic nuclei (MAGN) has been steadily growing thanks to a decade of continuous all-sky monitoring by the Fermi-Large Area Telescope (LAT). The recently released Fermi-LAT fourth catalogue of AGN includes over 50 MAGN objects. These sources allow us to investigate different...
Go to contribution page -
Elena Orlando13/04/2021, 15:15
Standard models of the large-scale interstellar emission officially adopted so far for studies of the Fermi-LAT data are very uncertain and show some discrepancies with respect to the data especially in the inner Galaxy where the degeneracy with the various components is large, underlining the necessity of more realistic models.
Go to contribution page
We focus here on the large-scale Inverse Compton (IC) component... -
Julie McEnery (NASA)13/04/2021, 15:30
The All sky Medium Energy Gamma-ray Observatory (AMEGO) is a probe class mission that will provide ground breaking new capabilities for multi-messenger astrophysics - identifying and studying the astrophysical objects that produce gravitational waves and neutrinos; along with a rich menu of additional science in astrophysical jets, compact objects, dark matter and nuclear line spectroscopy....
Go to contribution page -
Julian Sitarek (University of Lodz)13/04/2021, 15:30
The flat-spectrum radio quasar QSO B1420+326 underwent an enhanced gamma-ray flux state seen by Fermi-LAT at the turn of 2019/2020. Compared to the low state both the position and luminosity of the two spectral energy distribution peaks changed by at least two orders of magnitude. The high state resulted in the discovery of the very-high-energy (>100 GeV) gamma-ray emission from the source by...
Go to contribution page -
Tsunefumi Mizuno (Hiroshima University)13/04/2021, 15:30
An accurate estimate of the interstellar gas density distribution is crucial to understanding the interstellar medium (ISM) and Galactic cosmic rays (CRs). However, a significant amount of gas not traced properly by standard radio line surveys (``dark gas") has been preventing accurate measurement of the total neutral gas column density and CR intensity. To overcome this difficulty, we...
Go to contribution page -
Alexander Moiseev13/04/2021, 15:45
We present a novel concept for a next-generation γ-ray telescope that will cover the hard X-ray - soft γ-ray region. Despite the progress made by the European Space Observatory INTEGRAL, this energy range is still under-explored. GECCO will conduct high-sensitivity measurements of the cosmic γ-radiation in the energy range from 100 keV to ∼10 MeV and create intensity maps with high spectral...
Go to contribution page -
Luca Giunti13/04/2021, 15:45
The identification of active PeVatrons, hadronic particle accelerators reaching the knee (at the energy of few PeV), is crucial to understand the origin of cosmic rays in the Galaxy. In this context, we report on new H.E.S.S. observations of the PeVatron candidate HESSJ1702-420, close to the source 2FHL J1703.4-4145, that have revealed the presence of gamma-rays up to 100 TeV at 5 sigma...
Go to contribution page -
Markus Boettcher (North-West University)13/04/2021, 15:45
In recent work, we have developed a self consistent two-zone model of
Go to contribution page
time-dependent diffusive shock acceleration in the relativistic jets of
blazars and the resulting multi-wavelength spectral and variability
features. In this paper, we report the results of detailed fitting of
this model to recent multi-wavelength data from two blazars detected
during bright gamma-ray flares by... -
Haocheng Zhang13/04/2021, 16:00
Recent optical polarimetry monitoring programs have discovered optical polarization angle swings during blazar flares. Observations have shown that these swings are mostly simultaneous with Fermi gamma-ray flares. While angle swings are found in both flat spectrum radio quasars and BL Lac objects, blazars that have shown swings tend to be more active and brighter in gamma-rays. These features...
Go to contribution page -
Francesco Loparco (Universita e INFN, Bari (IT))13/04/2021, 16:00
The Large Area Telescope onboard the Fermi Gamma-ray Space Telescope has collected more than 15 millions of cosmic-ray electron and positron (CRE) events in the energy range from 42 GeV to 2 TeV in about 7.5 years since its launch in 2008. We have searched for possible features in the energy spectrum of Galactic CREs, which could be interpreted as a signature of the presence of a nearby dark...
Go to contribution page -
Tsuguo Aramaki13/04/2021, 16:00
GRAMS (Gamma-Ray and AntiMatter Survey) is a next-generation balloon/satellite mission that will be the first to target both MeV gamma-ray observations and antimatter-based indirect dark matter searches with a LArTPC detector. Astrophysical observations at MeV energies have not yet been well-explored due to the complexity and difficulties of the event reconstruction of Compton scatterings....
Go to contribution page -
Filippo D'Ammando13/04/2021, 16:15
The discovery by the Large Area Telescope on-board the Fermi satellite of variable gamma-ray emission from radio-loud narrow-line Seyfert 1 galaxies (NLSy1) revealed the presence of an emerging third class of AGN with powerful relativistic jets. Considering that NLSy1 are usually hosted in late-type galaxies with relatively small BH masses, this finding opened new challenging questions about...
Go to contribution page -
Francesco Longo13/04/2021, 16:15
Particle-detector arrays at high elevation, such as HAWC and LHAASO in the northern hemisphere, proved to be very effective instruments to perform surveys on a daily basis providing significant improvements on our knowledge about Very High Energy TeV gamma-ray sources. In this contribution, we will present an overview on the effort to realise a next generation gamma-ray survey observatory in...
Go to contribution page -
Martina Cardillo (INAF - Osservatorio astrofisico di Arcetri)13/04/2021, 16:15
Despite the enormous efforts done in very recent years, both theoretically and experimentally, the basic three questions about the CR origin remain without clear answers: what are their sources, how are they accelerated, how do they propagate?
Gamma-ray astronomy plays a fundamental role in this field. Both relativistic protons and electrons can emit in the gamma-ray band with different...
Go to contribution page -
Jason Hessels (University of Amsterdam)13/04/2021, 16:45
Fast radio bursts (FRBs) are millisecond-duration radio flashes of unknown physical origin. We now know that they originate at cosmological distances and hence must be exceptionally luminous. As such, FRBs promise to provide a new view of extreme astrophysics in action. At the same time, FRBs also promise to be unique probes of the ionised material within and between galaxies. Though only...
Go to contribution page -
Paula Benaglia13/04/2021, 17:10
A good fraction of high-energy (HE) sources do not have confirmed counterparts at any of the other branches of the electromagnetic spectrum. In the extragalactic sky, most of those sources with counterparts are blazars, the AGN subclass. HE sources with identified counterparts in our Galaxy do have a wide range of categories, as supernovae remnants, pulsar wind nebulae, microquasars, etc....
Go to contribution page -
Itumeleng Monageng13/04/2021, 17:35
Gamma-ray binary stars are intriguing members of the X-ray binary population which exhibit radiation across the entire electromagnetic spectrum, allowing for the study of extreme astrophysical conditions. They are characterised by a feature in their spectral energy distributions that shows a peak above 1 MeV. To date, there are only eight known systems which display a wide range of...
Go to contribution page -
Shawaiz Tabassum13/04/2021, 18:00
In the past decade, the most successful approach to search for millisecond pulsars (MSPs) has been to use acceleration searches to look for radio pulsations in the error bars of Gamma-ray sources identified by the Large Area Telescope (LAT) aboard the Fermi Satellite. However, 1000s of gamma-ray sources found by LAT still remain unassociated with any astrophysical object. It is believed that...
Go to contribution page -
Pieter van der Merwe13/04/2021, 18:00
In 2015 the advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO) detected the first ever gravitational event, gravitational wave event GW150914, with multiple new gravitational wave events, originating from both binary neutron stars and binary black hole (BBH) mergers, detected in subsequent years. In light of these detections, we simulate the dynamics of ambient test particles...
Go to contribution page -
Rahul Gupta13/04/2021, 18:04
We present the results of a detailed investigation of the prompt and afterglow emission in the High Energy Stereoscopic System(H.E.S.S.)-detected GRB190829A. Swift and Fermi observations of the prompt phase of this gamma-ray burst(GRB) reveal two isolated sub bursts or episodes, separated by a quiescent phase. The energetic and the spectral properties of the first episode are in stark contrast...
Go to contribution page -
Pablo Saz Parkinson (The University of Hong Kong)13/04/2021, 18:05
PSR J2021+4026 in the Cygnus region is one of the most interesting radio-quiet pulsars detected by Fermi-LAT. This source, thought to be associated with the Gamma Cygni supernova remnant, is the first isolated gamma-ray pulsar that exhibited clear evidence of variability, with a simultaneous flux and spindown change first occurred in October 2011. After a long recovery phase, in August 2015...
Go to contribution page -
Samuele Ronchini (Gran Sasso Science Institute)13/04/2021, 18:08
γ-ray bursts (GRBs) are cataclysmic events, whose role became central in the new multi-messenger era. GRBs are thought to originate from internal dissipation of the energy carried by ultra-relativistic jets launched by the remnant of a massive star’s death or a compact binary coalescence. In the present work I propose a novel investigation of the GRB emission mechanism, via time-resolved...
Go to contribution page -
Tinn Thongmeearkom13/04/2021, 18:10
In the last decade, Fermi LAT has provided an amazing roadmap to assist with pulsar searches conducted in other parts of the electromagnetic system. Indeed, multiple surveys have used Fermi unidentified sources with pulsar-like structures as their targets. Following this strategy, we present in this poster a survey conducted using the MeerKAT telescope to find energetic new pulsars associated...
Go to contribution page -
Sylvain Guiriec (NASA Goddard Space Flight Center / UMD / CRESST)13/04/2021, 18:12
Over the past few years, evidence has been accumulated in support of the existence of a thermal-like component during the GRB prompt phase. This component--often associated with the GRB jet's photosphere--is usually subdominant compared to a much stronger non-thermal one. The prompt emission of GRB 131014A detected by Fermi provides a unique opportunity to trace the history of this...
Go to contribution page -
Alessia Spolon13/04/2021, 18:15
PSR J0218+4232 is one of the most energetic millisecond pulsars (MSP) known and has been considered as one of the best candidates for very high energy (>100 GeV) γ-ray emission. It has a period of 2.3 ms in a 2-day orbit with a ∼ 0.2M⊙ white dwarf companion. With a characteristic age τ <0.5 Gyr it is one of the youngest MSPs known, with an extremely strong magnetic field at the light cylinder...
Go to contribution page -
Daniela Dorner13/04/2021, 18:16
Blazars are extremely variable sources showing flux variations on time scales from minutes to years. To study typical variability time scales of few hours to one day, continuous observations are crucial. Furthermore, studying the temporal evolution of the spectral energy distribution is a key to discriminate between different theoretical models for the emission mechanisms and processes...
Go to contribution page -
Maria Edvige Ravasio13/04/2021, 18:20
I will present the interesting case of GRB 190114C, the first GRB ever detected by MAGIC at Very High Energy (VHE). We analyzed the spectral evolution of its gamma-ray emission as detected by the Fermi Gamma-Ray Burst Monitor (GBM) up to∼60 s. We revealed the presence of an extra component starting on ∼4 s post-trigger. This extra component rises and decays quickly (peaking at∼6 s) and it is...
Go to contribution page -
Elena Orlando13/04/2021, 18:20
Gamma rays from the quiet Sun are produced by Cosmic Rays (CRs) interacting with its surface (disk component) and with its photon field (spatially extended inverse-Compton component, IC). IC is maximum close to the Sun and it extends over the whole sky. Monitoring the IC component with Fermi-LAT allows to obtain information on CR electrons close to the Sun and in the heliosphere for different...
Go to contribution page -
José Feliciano Agüí Fernández13/04/2021, 18:24
Short gamma-ray burst are, as we now know, produced as the result of the coalescence of two compact objects. These objects are also known to release large amounts of energy in gravitational waves during the merger. We present our first results on the study of GRB 160410A, an undoubtedly short GRB at z=1.717, making it one of the farthest short GRBs to date. We observed the afterglow emission...
Go to contribution page -
Alex McDaniel13/04/2021, 18:25
Wolf-Rayet (WR) stars are massive evolved stars undergoing advanced nuclear burning in their cores and possess strong stellar winds. WR stars -- and in particular WR binary systems -- are also predicted to be potential emitters of gamma rays. Although details of the high-energy emission mechanisms are not well-understood, a majority of the emission is likely due to strong shocks produced by...
Go to contribution page -
Antonio de Ugarte Postigo13/04/2021, 18:28
GRB 171205A was one of the closest GRBs that we have ever detected and one of the best-followed events. In this talk I will present the result of several studies of this event, its afterglow, associated supernova SN2017iuk, and host galaxy. Optical spectroscopy ranges from one hour after the event to more than 7 months later. These data served to identify cocoon signatures during the first 3...
Go to contribution page -
David Huber13/04/2021, 18:30
LS 5039 is one of the best-observed gamma-ray binaries with non-thermal emission ranging from soft X-rays to VHE gamma-ray. Explaining the observed anti-correlation between the X-ray/VHE and the HE gamma-ray bands, while accounting for its complex spectral features, has become a challenge for current modelling efforts.
Go to contribution page
We investigate this system in a wind-driven context, where non-thermal... -
Mariusz Tarnopolski13/04/2021, 18:32
Two classes of gamma-ray bursts (GRBs), short and long, have been confidently identified thus far and are prescribed to different physical scenarios. A third class, intermediate in duration, was suggested to be present in various catalogues based on a mixture-modelling with two or three Gaussian distributions of the log-durations, log(T90). This might not be an adequate model. An analysis of...
Go to contribution page -
Raniere Menezes (Universidade de São Paulo)13/04/2021, 18:35
The gamma-ray emission from stars is induced by the interaction of cosmic rays with stellar atmospheres and photon fields. This emission is expected to come in two components: a stellar disk emission, where gamma-rays are mainly produced in atmospheric showers generated by hadronic cosmic rays, and an extended halo emission, where the high density of soft photons in the surroundings of stars...
Go to contribution page -
Amit Kumar13/04/2021, 18:36
This poster presents data and analysis of SN 2010kd, a low-redshift (z = 0.101) H-deficient superluminous supernova (SLSN), based on ultraviolet/optical photometry and optical spectroscopy spanning between −28 and +193 days relative to B band maximum light. The B band light curve comparison of SN 2010kd with a subset of well-studied SLSNe at comparable redshifts indicates that it is a...
Go to contribution page -
Robin Corbet13/04/2021, 18:40
Superorbital periods in Roche-lobe overflowing X-ray binaries such as Her X-1 have been known for some time. These can be understood as being related to the presence of an accretion disk. However, more recently a number of HMXBs accreting from the wind of their supergiant companion, where the presence of a persistent accretion disk is unlikely, have also been found to show superorbital...
Go to contribution page -
Amar Aryan13/04/2021, 18:40
In this paper,we present the observed photo metric and spectroscopic properties of a
Go to contribution page
type Ib supernova (SN) SN2015ap. Our aim in this paper is to model a reliable progenitor for SN2015ap, which can undergo core-collapse and explain the observed properties
of this SN. Initially, this SN shows some broad-lined features like SN2008D and later
it shows features matching with normal type Ib... -
Saeeda Sajjad13/04/2021, 18:44
The second Fermi LAT GRB catalog presents the results for 186 Gamma Ray Bursts (GRBs) detected by the Fermi Large Area Telescope (LAT) between 2008 and 2018. Out of these, we select the GRBs with significant detection in the LAT and GBM during the T90 time interval. We further subdivide this population into four quartiles based on the fluence from the GBM and carry out joint GBM-LAT spectral...
Go to contribution page -
Colin Clark13/04/2021, 18:45
The ability of the Fermi Large Area Telescope to identify pulsar-like gamma-ray sources has sparked a huge increase in discoveries of "Spider" millisecond pulsar binaries (Black Widows and Redbacks). These systems are characterised by long radio eclipses due to scattering and absorption by diffuse intra-binary material that has been evaporated from the companion star's surface. Unlike radio...
Go to contribution page -
Shashi Bhushan Pandey13/04/2021, 18:48
TeV emissions from Gamma-ray bursts (GRBs) are very important to study the origin and the radiation mechanisms in detail. Recent discoveries of TeV photons in some of the GRBs are challenging to be explained by Synchrotron mechanism. In this work, we present the results of a detailed investigation of the prompt and afterglow emission of recently discovered TeV GRBs (GRB 180720B, GRB 190114C...
Go to contribution page -
Robert Brose13/04/2021, 18:50
Supernova remnants are known to accelerate cosmic rays on account of their non-thermal emission of radio waves, X-rays, and gamma rays. However, the ability to accelerate cosmic-rays up to PeV-energies has yet to be demonstrated. The presence of cut-offs in the gamma-ray spectra of several young SNRs led to the idea that PeV-energies might only be achieved during the very initial stages of a...
Go to contribution page -
Tynik Idrissova13/04/2021, 18:52
For research, our group uses an installation with an area of 55 m2, consisting of two recording levels, gamma and hadron blocks, separated by a two-meter gap, located at the Tien Shan high-altitude scientific station. The main idea is to select interactions that are only observed in the gamma block, and not observed in the hadron block.
Go to contribution page
The upgraded ionization calorimeter with a field of... -
Robert Brose13/04/2021, 18:55
Supernova remnants are known to accelerate particles to relativistic energies on account of their non-thermal emission. The observational progress from radio to gamma-ray observations reveals more and more morphological features that need to be accounted for when modeling the emission from those objects.
Go to contribution page
We use our time-dependent acceleration code RATPaC to study the formation of extended... -
Alessandro Carosi, Alicia Lopez, Francesco Longo13/04/2021, 18:56
The Cherenkov Telescope Array (CTA) will be the next generation very high-energy (VHE) gamma-ray observatory. It will improve the sensitivity of current VHE instruments up to an order of magnitude and will cover the energy range from 20 GeV to at least 300 TeV. With its sensitivity, it will explore high redshift sources and extreme accelerators and will give access to the shortest timescale...
Go to contribution page -
Daniela Dorner13/04/2021, 19:00
Operational since October 2011, the First G-APD Cherenkov Telescope
Go to contribution page
(FACT) has been monitoring TeV-blazars. An unbiased observing strategy,
robotic operation and the usage of solid state photo sensors (SiPM, aka
G-APDs) increase the instrument's duty cycle and minimize observational
gaps, making FACT an ideal instrument for long-term monitoring. In more
than eight years, an unprecedented... -
Iurii Sushch (Deutsches Elektronen-Synchrotron DESY)13/04/2021, 19:00
Supernova remnants (SNRs) are widely believed to be one of the main candidates for the origin of Galactic cosmic rays. Very-high-energy gamma-ray emission observed from a number of SNRs suggests that particles are indeed accelerated to high energies by shock in remnants. However, it is extremely difficult to discriminate which particles are responsible for this emission as both protons...
Go to contribution page -
Antonios Nathanail13/04/2021, 19:04
We perform three-dimensional (3D) general-relativistic magnetohydrodynamic sim-
Go to contribution page
ulations to model the jet break-out from the ejecta expected to be produced in a
binary neutron-star merger. The structure of the relativistic outflow from the 3D sim-
ulation confirms our previous results from 2D simulations, namely, that a relativistic
magnetized outflow breaking out from the merger ejecta... -
Anabella Araudo13/04/2021, 19:05
Synchrotron radio emission from non-relativistic jets powered by massive protostars has been reported, indicating the presence of relativistic electrons and mG magnetic fields. We study diffusive shock acceleration and magnetic field amplification in protostellar jets with speeds between 300 and 1000 km/s. We show that the magnetic field in the synchrotron emitter can be amplified by the...
Go to contribution page -
Daniel Kerszberg (IFAE - Institute for High Energy Physics)13/04/2021, 19:08
On January 14th 2019, MAGIC, a stereoscopic system of two 17m diameter Imaging Atmospheric Cherenkov Telescopes located on the Canary island of La Palma, observed for the first time a gamma-ray burst (GRB) at TeV energies, namely GRB 190114C. MAGIC measurements started ~60s after the onset of GRB 190114C, predominantly in the featureless smooth afterglow phase. Nevertheless, in the first 30s...
Go to contribution page -
Drikus Plooy13/04/2021, 19:10
Gamma-ray binaries are a class of high-mass binary systems which are distinguished by their spectral energy distributions peaking above 1 MeV. Gamma-ray binaries consist of an O or B type companion and an orbiting compact object which is either a neutron star or a black hole. Generally in these systems the nature of the compact object is unknown except for two cases, namely PSR B1259-63 and...
Go to contribution page -
Peter Veres13/04/2021, 19:12
We present the observations of the first unambiguous magnetar giant flare from outside of our galactic neighborhood. At the beginning, GRB 200415A was identified as a short GRB, but upon further investigation and observations from additional instruments, we concluded this event was a giant flare from a magnetar located in the Sculptor galaxy, 3.5 Mpc away. The GBM lightcurve shows very fast...
Go to contribution page -
Constantinos Kalapotharakos (UMCP CRESST / NASA GSFC)13/04/2021, 19:15
The Fermi data imply that the gamma-ray observables, i.e., the gamma-ray luminosity, spectral cut-off energy, stellar surface magnetic field, and spin-down power obey a relation that represents a 3D plane in the 4D log-space. This observed fundamental plane (FP) is remarkably close to the theoretical relation that is obtained, assuming that the pulsar gamma-ray emission is due to curvature...
Go to contribution page -
Vidushi Sharma13/04/2021, 19:16
The nature of the gamma-ray burst (GRB) central engine remains an enigma. Entities widely considered to be capable of powering the extreme jets are: (i) a hyper-accreting stellar-mass black hole, and (ii) a rapidly spinning, highly magnetized, neutron star (NS) or fast magnetar. The maximum rotational energy that is feasible in a millisecond magnetar to form a jet is ~10^52 erg and hence...
Go to contribution page -
Isabella Mereu14/04/2021, 07:00
Gamma-ray catalogs produced with data of the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope typically integrate years of exposure. Since Active Galactic Nuclei (AGNs) are characterized by strong and fast variability, their emission is diluted by long-time data integration. Transient sources can be more easily detected over short time scales. In order to search for...
Go to contribution page -
Pieter van der Merwe14/04/2021, 07:00
In 2015 the advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO) detected the first ever gravitational event, gravitational wave event GW150914, with multiple new gravitational wave events, originating from both binary neutron stars and binary black hole (BBH) mergers, detected in subsequent years. In light of these detections, we simulate the dynamics of ambient test particles...
Go to contribution page -
Mariusz Tarnopolski14/04/2021, 07:03
Two classes of gamma-ray bursts (GRBs), short and long, have been confidently identified thus far and are prescribed to different physical scenarios. A third class, intermediate in duration, was suggested to be present in various catalogues based on a mixture-modelling with two or three Gaussian distributions of the log-durations, log(T90). This might not be an adequate model. An analysis of...
Go to contribution page -
Saeeda Sajjad14/04/2021, 07:06
The second Fermi LAT GRB catalog presents the results for 186 Gamma Ray Bursts (GRBs) detected by the Fermi Large Area Telescope (LAT) between 2008 and 2018. Out of these, we select the GRBs with significant detection in the LAT and GBM during the T90 time interval. We further subdivide this population into four quartiles based on the fluence from the GBM and carry out joint GBM-LAT spectral...
Go to contribution page -
Naomi Tsuji14/04/2021, 07:07
We report the results of cross-match between the hard X-ray and GeV gamma-ray catalogs, by making use of the latest 105-month Swift/BAT and 10-yr Fermi/LAT catalogs, respectively. We found 181 matched sources in total, which include 36 of false-match, unidentified, and ambiguous sources. The firmly matched sources consist of blazars (> 60%), pulsars and pulsar wind nebulae (∼10%), radio...
Go to contribution page -
Alessandro Carosi, Alicia Lopez, Francesco Longo14/04/2021, 07:09
The Cherenkov Telescope Array (CTA) will be the next generation very high-energy (VHE) gamma-ray observatory. It will improve the sensitivity of current VHE instruments up to an order of magnitude and will cover the energy range from 20 GeV to at least 300 TeV. With its sensitivity, it will explore high redshift sources and extreme accelerators and will give access to the shortest timescale...
Go to contribution page -
Rahul Gupta14/04/2021, 07:12
We present the results of a detailed investigation of the prompt and afterglow emission in the High Energy Stereoscopic System(H.E.S.S.)-detected GRB190829A. Swift and Fermi observations of the prompt phase of this gamma-ray burst(GRB) reveal two isolated sub bursts or episodes, separated by a quiescent phase. The energetic and the spectral properties of the first episode are in stark contrast...
Go to contribution page -
Elena Orlando14/04/2021, 07:14
The Fermi Large Area Telescope (LAT) has been detecting hundreds of Galactic sources, most of which are pulsars. Many Galactic sources are still undetected or unresolved due to their low flux, below the Fermi LAT sensitivity, or because of foreground and source confusion. Moreover, among the many unassociated sources, which are one third of the detected sources, a large amount may have...
Go to contribution page -
Daniela Dorner14/04/2021, 07:15
Operational since October 2011, the First G-APD Cherenkov Telescope
Go to contribution page
(FACT) has been monitoring TeV-blazars. An unbiased observing strategy,
robotic operation and the usage of solid state photo sensors (SiPM, aka
G-APDs) increase the instrument's duty cycle and minimize observational
gaps, making FACT an ideal instrument for long-term monitoring. In more
than eight years, an unprecedented... -
Peter Veres14/04/2021, 07:18
We present the observations of the first unambiguous magnetar giant flare from outside of our galactic neighborhood. At the beginning, GRB 200415A was identified as a short GRB, but upon further investigation and observations from additional instruments, we concluded this event was a giant flare from a magnetar located in the Sculptor galaxy, 3.5 Mpc away. The GBM lightcurve shows very fast...
Go to contribution page -
Luca Giunti14/04/2021, 07:21
The identification of active PeVatrons, hadronic particle accelerators reaching the knee (at the energy of few PeV), is crucial to understand the origin of cosmic rays in the Galaxy. In this context, we report on new H.E.S.S. observations of the PeVatron candidate HESSJ1702-420, close to the source 2FHL J1703.4-4145, that have revealed the presence of gamma-rays up to 100 TeV at 5 sigma...
Go to contribution page -
Vidushi Sharma14/04/2021, 07:21
The nature of the gamma-ray burst (GRB) central engine remains an enigma. Entities widely considered to be capable of powering the extreme jets are: (i) a hyper-accreting stellar-mass black hole, and (ii) a rapidly spinning, highly magnetized, neutron star (NS) or fast magnetar. The maximum rotational energy that is feasible in a millisecond magnetar to form a jet is ~10^52 erg and hence...
Go to contribution page -
Samuele Ronchini (Gran Sasso Science Institute)14/04/2021, 07:24
γ-ray bursts (GRBs) are cataclysmic events, whose role became central in the new multi-messenger era. GRBs are thought to originate from internal dissipation of the energy carried by ultra-relativistic jets launched by the remnant of a massive star’s death or a compact binary coalescence. In the present work I propose a novel investigation of the GRB emission mechanism, via time-resolved...
Go to contribution page -
Antonios Nathanail14/04/2021, 07:27
We perform three-dimensional (3D) general-relativistic magnetohydrodynamic sim-
Go to contribution page
ulations to model the jet break-out from the ejecta expected to be produced in a
binary neutron-star merger. The structure of the relativistic outflow from the 3D sim-
ulation confirms our previous results from 2D simulations, namely, that a relativistic
magnetized outflow breaking out from the merger ejecta... -
Alejandra Aguirre-Santaella14/04/2021, 07:28
TeV DM candidates are gradually earning more and more attention within the community. Among others, extra-dimensional brane-world models may produce thermal DM candidates with masses up to 100 TeV, which could be detected with the next generation of very-high-energy gamma-ray observatories such as the Cherenkov Telescope Array (CTA).
Go to contribution page
In this work, we study the sensitivity of CTA to branon DM... -
Daniel Kerszberg (IFAE - Institute for High Energy Physics)14/04/2021, 07:30
On January 14th 2019, MAGIC, a stereoscopic system of two 17m diameter Imaging Atmospheric Cherenkov Telescopes located on the Canary island of La Palma, observed for the first time a gamma-ray burst (GRB) at TeV energies, namely GRB 190114C. MAGIC measurements started ~60s after the onset of GRB 190114C, predominantly in the featureless smooth afterglow phase. Nevertheless, in the first 30s...
Go to contribution page -
Tynik Idrissova14/04/2021, 07:33
For research, our group uses an installation with an area of 55 m2, consisting of two recording levels, gamma and hadron blocks, separated by a two-meter gap, located at the Tien Shan high-altitude scientific station. The main idea is to select interactions that are only observed in the gamma block, and not observed in the hadron block.
Go to contribution page
The upgraded ionization calorimeter with a field of... -
Jeremy Hare14/04/2021, 07:35
The release of the Fermi-LAT 4FGL catalog includes over 1,000 unidentified Fermi-LAT sources (roughly 25% of sources). One of the most successful ways to uncover their counterparts are through X-ray observations. Over their ~20 year lifetimes XMM-Newton and Chandra have observed a large number of Galactic fields, many of which contain unidentified Galactic Fermi-LAT sources. Often these fields...
Go to contribution page -
Sylvain Guiriec (NASA Goddard Space Flight Center / UMD / CRESST)14/04/2021, 07:36
Over the past few years, evidence has been accumulated in support of the existence of a thermal-like component during the GRB prompt phase. This component--often associated with the GRB jet's photosphere--is usually subdominant compared to a much stronger non-thermal one. The prompt emission of GRB 131014A detected by Fermi provides a unique opportunity to trace the history of this...
Go to contribution page -
Shashi Bhushan Pandey14/04/2021, 07:39
TeV emissions from Gamma-ray bursts (GRBs) are very important to study the origin and the radiation mechanisms in detail. Recent discoveries of TeV photons in some of the GRBs are challenging to be explained by Synchrotron mechanism. In this work, we present the results of a detailed investigation of the prompt and afterglow emission of recently discovered TeV GRBs (GRB 180720B, GRB 190114C...
Go to contribution page -
Geoff Beck14/04/2021, 07:42
Gamma-ray probes have historically been a gold-standard in indirect dark matter detection due to their smaller set of complicating factors and generally lower backgrounds. However, they are most optimally sensitive to the traditional supersymmetric WIMP annihilation channels and leptophilic channels (particularly for larger masses) are much harder to probe effectively in this manner. However,...
Go to contribution page -
Amit Kumar14/04/2021, 07:42
This poster presents data and analysis of SN 2010kd, a low-redshift (z = 0.101) H-deficient superluminous supernova (SLSN), based on ultraviolet/optical photometry and optical spectroscopy spanning between −28 and +193 days relative to B band maximum light. The B band light curve comparison of SN 2010kd with a subset of well-studied SLSNe at comparable redshifts indicates that it is a...
Go to contribution page -
Daniela Dorner14/04/2021, 07:45
Blazars are extremely variable sources showing flux variations on time scales from minutes to years. To study typical variability time scales of few hours to one day, continuous observations are crucial. Furthermore, studying the temporal evolution of the spectral energy distribution is a key to discriminate between different theoretical models for the emission mechanisms and processes...
Go to contribution page -
Antonio de Ugarte Postigo14/04/2021, 07:48
GRB 171205A was one of the closest GRBs that we have ever detected and one of the best-followed events. In this talk I will present the result of several studies of this event, its afterglow, associated supernova SN2017iuk, and host galaxy. Optical spectroscopy ranges from one hour after the event to more than 7 months later. These data served to identify cocoon signatures during the first 3...
Go to contribution page -
Pablo Saz Parkinson (The University of Hong Kong)14/04/2021, 07:49
The Fermi LAT Fourth Source Catalog (4FGL) contains over 5000 gamma-ray sources detected using 8 years of LAT data. Among these sources, over 3000 are associated with known blazars, 239 are associated with pulsars, and over 1300 are classified as 'unassociated' sources, meaning they have no known plausible counterpart at any other wavelength. Following on our previous work on the 3FGL Catalog...
Go to contribution page -
Amar Aryan14/04/2021, 07:51
In this paper,we present the observed photo metric and spectroscopic properties of a
Go to contribution page
type Ib supernova (SN) SN2015ap. Our aim in this paper is to model a reliable progenitor for SN2015ap, which can undergo core-collapse and explain the observed properties
of this SN. Initially, this SN shows some broad-lined features like SN2008D and later
it shows features matching with normal type Ib... -
José Feliciano Agüí Fernández14/04/2021, 07:54
Short gamma-ray burst are, as we now know, produced as the result of the coalescence of two compact objects. These objects are also known to release large amounts of energy in gravitational waves during the merger. We present our first results on the study of GRB 160410A, an undoubtedly short GRB at z=1.717, making it one of the farthest short GRBs to date. We observed the afterglow emission...
Go to contribution page -
Michael Sarkis14/04/2021, 07:56
Recent studies of the effects on the Earth’s atmosphere by astrophysical sources, such as nearby gamma-ray bursts or supernovae, have shown that these events could lead to severe changes in atmospheric composition. Depletion of ozone, the most notable of these changes, is extremely dangerous to living organisms as any decrease in ozone levels leads to an increase in the irradiance of harmful...
Go to contribution page -
Maria Edvige Ravasio14/04/2021, 07:57
I will present the interesting case of GRB 190114C, the first GRB ever detected by MAGIC at Very High Energy (VHE). We analyzed the spectral evolution of its gamma-ray emission as detected by the Fermi Gamma-Ray Burst Monitor (GBM) up to∼60 s. We revealed the presence of an extra component starting on ∼4 s post-trigger. This extra component rises and decays quickly (peaking at∼6 s) and it is...
Go to contribution page -
Nicola Omodei14/04/2021, 15:00
In the last decade, the number of known gamma-ray sources has exploded and gamma-ray astronomy is reaching an era of precision measurements. Wide-field-of-view observatories like Fermi-LAT in the GeV range and HAWC in the TeV range, as well as IACTs like H.E.S.S., MAGIC, and VERITAS, have amassed a wealth of data. Some of these experiments have made data and analysis tools available to the...
Go to contribution page -
Jean Ballet (CEA Saclay)14/04/2021, 15:25
The latest Fermi-LAT source catalog constructed from scratch (4FGL: 5065 sources above 50 MeV) was based on eight years (2008 - 2016) of Pass 8 data. Since neither the event reconstruction (Pass 8) nor the interstellar emission model (gll_iem_v07) has evolved since then, we decided we will provide incremental 4FGL releases at regular intervals of two years, until one of those two key...
Go to contribution page -
Adam Goldstein14/04/2021, 15:40
The Fermi Gamma-ray Burst Monitor (GBM) observes a wide variety of high-energy phenomena, spanning astrophysics, heliophysics, and Earth science. Its all-sky monitoring, broad energy range, fine spectral resolution, and fine time resolution make GBM a promising instrument for many different investigations. The GBM Team developed spectral analysis software, RMfit, for the analysis of onboard...
Go to contribution page -
Dan Kocevski14/04/2021, 15:55
We present the Fermi LAT light curve repository, consisting of a public library of light curves for variable Fermi LAT sources on a variety of time scales. Based on the successful Fermi All-sky Variability Analysis data portal, the Fermi LAT light curve repository aims to provide publication quality light curves on time scales of days, weeks, and months for over 1500 sources deemed variable in...
Go to contribution page -
Elisabetta Bissaldi14/04/2021, 16:10
The Fermi Masterclass is an international outreach event designed to give high-school students the unique opportunity to discover the world of High-Energy Astrophysics. Since 2017, following analogous experiences previously proposed mostly in France, various Italian universities and research institutes, guided by the National Institute for Nuclear Physics (INFN), organized a "full immersion"...
Go to contribution page -
David Paneque14/04/2021, 16:35
The Active Galactic Nuclei (AGN) are the most powerful persistent sources in the Universe, bringing information from extreme environments expected to accelerate particles to energies well above those at reach on Earth-based laboratories. In the last decade, the advent of novel instrumentation has boosted our capabilities to study these environments across the electromagnetic spectrum. Such...
Go to contribution page -
Justin Finke14/04/2021, 17:00
Gamma-rays from cosmological gamma-ray sources, primarily blazars but also gamma-ray bursts, interact with the extragalactic background light (EBL) photons, and are absorbed. This allows one to use gamma-ray absorption to constrain the EBL, which depends strongly on a number of quantities that are interesting from an astrophysical and cosmological point of view. This includes the universe's...
Go to contribution page -
Markus Ahlers (Niels Bohr International Academy, Niels Bohr Institute)14/04/2021, 17:25
The IceCube neutrino observatory at the geographic South Pole has been operating at full capacity for the past ten years. In 2013, IceCube reported first evidence of an isotropic flux of astrophysical neutrinos in the TeV-PeV energy range. While the flux is by now observed with high significance, its astrophysical origin is unknown. Only recently, IceCube was able to report first compelling...
Go to contribution page -
Anita Reimer (University of Innsbruck)14/04/2021, 17:50
Multi-messenger astrophysics experienced a tremendous boost, after the first detection of astrophysical neutrinos was reported eight years ago. Despite having uncovered a large variety of gamma-ray emitting source classes up to today, a firm identification of the dominant source population responsible for the detected high-energy neutrino all-sky flux is, however, still lacking.
Go to contribution page
In this... -
Dr Andreas von Kienlin (MPE)14/04/2021, 18:15
With the completion of the first decade of operation, Fermi-GBM has been longer in orbit than its predecessor experiment BATSE on-board CGRO. It is capable to detect almost the same number of GRBs (~240 GBM GRBs compared ~300 BATSE GRBs per year) resulting in 2357 triggers on cosmic GRBs during the first ten years. The GBM GRB catalog series is now continued by the latest releases of the GBM...
Go to contribution page -
Joshua Wood (University of Wisconsin, Madison)14/04/2021, 18:15
The simultaneous detection of a high energy neutrino event during a gamma-ray flare from TXS 0506+056 played an essential role in its identification as an astrophysical neutrino source in 2017. This highlights the current importance of electromagnetic follow-up by gamma-ray instruments for finding new sources in the field of high-energy neutrino astronomy where many of the sources and source...
Go to contribution page -
Marianne Lemoine-Goumard (CNRS)14/04/2021, 18:15
Cosmic rays are mostly composed by protons accelerated to relativistic speeds. When those protons encounter interstellar material, they produce neutral pions which in turn decay into gamma rays. This offers a compelling way to identify the acceleration sites of protons. A characteristic hadronic spectrum was detected in the gamma-ray spectra of four Supernovae Remnants (SNRs), IC 443, W44,...
Go to contribution page -
Stefano Ciprini (INFN & University Perugia)14/04/2021, 18:30
The Fermi Flare Advocate (also known as Gamma-ray Sky Watcher, FA-GSW) service provides for a quick look and review of the gamma-ray sky observed daily by the Fermi Large Area Telescope (LAT) through on-duty LAT Flare Advocates and high level software pipelines like the LAT Automatic Science Processing (ASP), the Fermi All-sky Variability Analysis (FAVA), a dedicated suite of software and,...
Go to contribution page -
Felix Ryde14/04/2021, 18:30
A large fraction of gamma-ray burst (GRB) spectra are very hard below the peak which indicates that the emission comes from the photosphere. The size of this fraction is investigated in two different ways. First, we use the theoretical spectrum expected from a non-dissipative flow to make synthetic Fermi/GBM spectra which are then fitted by the cut off power law function to simulate real...
Go to contribution page -
Francesco de Palma (INFN)14/04/2021, 18:30
Supernova Remnants (SNRs) emitting gamma rays in the GeV-TeV energy range are fundamental for identifying the accelerators of Galactic cosmic rays. In 2018 H.E.S.S. has revealed at TeV energies three extended shell-like sources: HESS J1534-571, HESS J1614-518 and HESS J1912+101. A radio Supernova Remnant (SNR) candidate has been identified as a counterpart to HESS J1534-571, therefore it is...
Go to contribution page -
Justine Devin14/04/2021, 18:45
The supernova remnant (SNR) G150.3+4.5 was recently detected in radio and exhibits a shell-like morphology with an angular size of 3°, suggesting either an old or a nearby SNR. An extended Fermi-LAT source, spatially coincident with the radio SNR, was reported in the Fermi Galactic Extended Source Catalog. Using more than 10 years of Fermi-LAT data, we perform detailed morphological and...
Go to contribution page -
Virginia Cunningham14/04/2021, 18:45
Gamma-ray bursts (GRBs) detected by the Large Area Telescope (LAT) on board Fermi tend to be extraordinarily bright, making them ideal candidates for exploring emission models beyond the traditional on-axis, top-hat jet model. In this talk I will discuss our recent work modeling GRB 160625B with alternative jet structure shapes and testing assumptions typically made regarding certain physical...
Go to contribution page -
Simone Garrappa14/04/2021, 18:45
The detection of the flaring gamma-ray blazar TXS 0506+056 in spatial and temporal coincidence with the high-energy neutrino IC-170922A represents a milestone for multi-messenger astronomy. This finding suggests that gamma rays represent an important tracer of neutrino production in blazars and the 11-year all-sky coverage of the Fermi-LAT provides unique opportunities for both long-term...
Go to contribution page -
Maxim Lyutikov14/04/2021, 19:00
We develop a model of early GRB X-ray afterglows are dominated by emission from the reverse shock propagating in highly relativistic, highly magnetized wind of a long-lasting central engine, similar to the Pulsar Wind Nebulae. The model reproduces high conversion efficiency of the wind power into radiation (fast cooling regime), afterglow plateaus, flares and abrupt intensity drops. The ...
Go to contribution page -
Weidong Jin (The University of Alabama)14/04/2021, 19:00
VERITAS, an array of atmospheric-Cherenkov telescopes sensitive to gamma rays in the very-high-energy range (VHE, E > 100 GeV), carries out an extensive multimessenger program focused on the search for electromagnetic counterparts to high-energy neutrinos and gravitational waves. As both neutrinos and gamma rays are expected to be produced in hadronic interactions near cosmic ray accelerators,...
Go to contribution page -
Emma de Ona Wilhelmi14/04/2021, 19:00
Recent results obtained with gamma-ray satellites have established supernova remnants as accelerators of GeV hadronic cosmic rays. In such processes, CRs accelerated in SNR shocks interact with particles from gas clouds in their surrounding. In particular, the rich medium in which core-collapse SNRs explode provides a large target density to boost hadronic gamma-rays. SNR G39.2-0.3 is one of...
Go to contribution page -
Robert Brose14/04/2021, 19:15
Supernova remnants are known to accelerate cosmic rays on account of their non-thermal emission of radio waves, X-rays, and gamma rays. Although there are many models for the acceleration of cosmic rays in Supernova remnants, the escape of cosmic rays from these sources is yet understudied.
Go to contribution page
We use our time-dependent acceleration code RATPaC to study the acceleration of cosmic rays and their... -
Rachel Hamburg14/04/2021, 19:15
Cosmological Gamma-Ray Bursts (GRBs) are known to arise from neutron star mergers and collapsars. We have identified 4 GRBs within 5 Mpc which are inconsistent with such an origin: they appear to be extragalactic Magnetar Giant Flares (MGFs). These are the closest known GRBs, the signals from the most distant known magnetars, and suggest a broadly morphology of MGFs than previously known. They...
Go to contribution page -
Foteini Oikonomou14/04/2021, 19:15
Blazars host relativistic jets which are considered to be excellent sites for high-energy-cosmic-ray acceleration. In the vicinity of the supermassive black hole and inside the relativistic jet, there exist photon fields which are thought to facilitate high-energy neutrino production. Recently, a number of blazars have been tentatively associated with high-energy neutrinos detected by the...
Go to contribution page -
Niccolo' Di Lalla14/04/2021, 19:30
Magnetars are neutron stars with the strongest-known magnetic fields in the Universe, up to a thousand times stronger than typical neutron stars. Rarely, magnetars can produce enormous eruptions, called giant flares, consisting of a highly luminous sub-second initial spike of hard X-rays and soft gamma rays, followed by a softer and much dimmer pulsating tale lasting a few hundred...
Go to contribution page -
Samayra Straal14/04/2021, 19:30
Pulsar wind nebulae (PWNe) are created by the interaction between the highly relativistic winds from pulsars and their surroundings. When young, the PWN resides in the remnant produced by the supernova explosion, and confines the entire energy input of the pulsar. These PWNe also prove to be excellent particle accelerators. Hence, the properties of these systems can be used to study the...
Go to contribution page -
Michela Negro14/04/2021, 19:30
The new era of the multi-messenger Astrophysics has begun. The first step required to enable this science is to identify the multimessenger sources. Of particular interest is the relation between the high-energy neutrino events detected by IceCube Observatory and the γ-ray emission from extra-galactic objects. Despite the effort devoted to finding a clear γ-ray counterpart to astrophysical...
Go to contribution page -
Stefan Larsson15/04/2021, 07:00
We present the results of twelve years of Fermi Large Area Telescope (LAT) monitoring observations of the high-energy peaked BL Lac object PG 1553+113. The Fermi-LAT (E>100 MeV) results are complemented by simultaneous, multi-wavelength data at lower energy bands, including the optical band. Our previous work published in 2015 revealed the presence of a ~2 years periodic modulation in the...
Go to contribution page -
Lars Nieder15/04/2021, 07:00
Fermi gamma-ray source lists have led to the discovery of many "spider" pulsars, tight binary systems in which the pulsars are evaporating their companions. Most of these have been found in radio searches targeting the Fermi sources, because the computational effort to find the pulsations by directly searching the gamma-ray data is tremendous. Using novel search methods, optical observations...
Go to contribution page -
Magnus Axelsson15/04/2021, 07:00
Since their discovery over 50 years ago, Gamma-Ray Bursts (GRBs) have mainly been observed up to a few MeV. In recent years, several detections have been made in the very high-energy domain by ground-based Cherenkov Telescopes, providing new input and raising new questions regarding the emission mechanisms of these powerful events. The Fermi-LAT, spanning the energy range from tens of MeV to...
Go to contribution page -
Pablo Peñil (Universidad Complutense de Madrid)15/04/2021, 07:15
Blazars can show variability on a wide range of timescales. However, the search for periodicity in the gamma-ray emission of blazars remains an on-going challenge. This contribution will show the results obtained when a systematic pipeline is used to implement ten well-established methods for searching for periodicity. We analyze the most promising candidates selected from our previous work,...
Go to contribution page -
Makoto Arimoto (Kanazawa University)15/04/2021, 07:15
We report on the observations by Fermi and Swift of gamma-ray burst (GRB) 190114C detected at very high energy by MAGIC. The prompt gamma-ray emission was detected by the Fermi/GBM, the Fermi/LAT, and the Swift/BAT and the long-lived afterglow emission was subsequently observed by the GBM, LAT, Swift/XRT, and Swift/UVOT. The early-time observations reveal multiple emission components that...
Go to contribution page -
Pablo Saz Parkinson (The University of Hong Kong)15/04/2021, 07:15
The Fermi Large Area Telescope (LAT) has detected ~250 gamma-ray pulsars in its > 10 years of operation. The gamma-ray emission from most of these pulsars peaks in the GeV range, where the LAT is most sensitive; perhaps not surprisingly, only a handful of them fall in the "soft" gamma-ray category. While Fermi pulsars are teaching us much about the pulsar mechanism, the full picture is still...
Go to contribution page -
Michael Kreter15/04/2021, 07:30
Blazars are powered by super-massive black holes in their centers and are known for extreme variability on time scales from minutes to years. In case of a binary black hole system, this duality is traceable as periodic modulation of their gamma-ray emission. So far, high-significance periodicity has been reported for a very few blazars with standard approaches.
Go to contribution page
We developed a method to search... -
Monica Barnard15/04/2021, 07:30
The ground-based discovery of pulsed $\gamma$-ray emission from four pulsars has marked the beginning of a new era in pulsar science. Recent kinetic simulations sparked a debate regarding the emission mechanism responsible for pulsed $\gamma$-ray emission from pulsars. Detection of the Vela pulsar up to $\sim$~100 GeV by H.E.S.S.\ and Fermi Large Area Telescope (LAT) provides evidence for a...
Go to contribution page -
Sylvia Zhu15/04/2021, 07:30
The field of gamma-ray bursts (GRBs) is often advanced by detections of spectacular individual events. Most recently, H.E.S.S. detected VHE emission from GRB 190829A for three consecutive nights, up to 56 hours after the burst began, providing an unprecedented opportunity to study the late-time VHE afterglow spectrum. By combining the simultaneous Swift-XRT and H.E.S.S. observations, some...
Go to contribution page -
Fidy Andriamanankasina Ramamonjisoa15/04/2021, 07:45
We report the modelling of the optical polarized emission of the white dwarf pulsar in the binary system AR Scorpii (AR Sco) in the framework of the striped pulsar wind model constrained by optical photopolarimetric data. One of the main goals of this work is to constrain the parameters, which describe the white dwarf pulsar magnetic field geometry. Besides, we determine the location of the...
Go to contribution page -
RIleyAnne Sharpe15/04/2021, 07:45
The origin of the diffuse isotropic gamma-ray back- ground measured by the Fermi gamma-ray satellite at energies between 100 MeV and 820 GeV remains largely uncertain. Population studies indicate that most of the emission originates in a large number of extragalactic objects such as active galactic nuclei, star-forming galaxies, or radio galaxies too faint to be resolved as individual sources....
Go to contribution page -
Christina Thöne15/04/2021, 07:45
GRB 190114C was the first gamma-ray burst (GRB) for which a secure detection of very high-energy (VHE) photons by MAGIC has been announced. By now, at least another two GRBs have confirmed VHE detections. One of the still unsolved questions is whether all GRBs show VHE emission (and we were just lucky to observe it) or whether they actually require special conditions for this VHE emission to...
Go to contribution page -
Louis Du Plessis15/04/2021, 08:00
Marsh et al. (2016; M16) detected radio and optical pulsations from the binary system AR Scorpii (AR Sco). This system, with an orbital period of 3.55h, is composed of a cool, low-mass star and a white dwarf with a spin period of 1.95min. X-ray pulsations have also been detected from this source (Takata et al. 2018). Optical observations by Buckley et al. (2017) showed that optical pulsations...
Go to contribution page -
Asaf Pe'er15/04/2021, 08:00
The acceleration site of ultra-high energy cosmic rays is still an open question despite extended research.
Over 20 years ago it was proposed that gamma-ray bursts (GRBs) are good candidates. This idea can now better be tested using recent Fermi data of GRB prompt emission spectra, that can be used to put strong constraints on the physical conditions of the outflow.I will critically...
Go to contribution page -
Sarah White15/04/2021, 08:00
Powerful radio-galaxies feature heavily in our understanding of galaxy evolution. However, when it comes to studying their properties as a function of redshift and/or environment, the most-detailed studies tend to be limited by small-number statistics. In this talk, I will present a new sample of ~2,000 of the ‘brightest’ radio-sources in the southern sky (Dec. < 30 deg). These were observed...
Go to contribution page -
Zachary Weaver15/04/2021, 08:15
We analyze the parsec-scale jet kinematics of a sample of gamma-ray bright blazars monitored roughly monthly with the Very Long Baseline Array at 43 GHz from 2007 to 2018. We implement a novel piece-wise linear fit to the trajectories of over 500 distinct emission features (knots) in the jets of 23 quasars, 12 BL Lacertae objects, and 3 radio galaxies. The apparent speeds range from < 1c to...
Go to contribution page -
Mariusz Tarnopolski15/04/2021, 08:15
We searched for coincident arrivals of photons from gamma-ray bursts (GRBs) and ultra-high energy neutrinos (UHENs) from the IceCube Observatory. A spatiotemporal cross-match of the compiled datasets that contained 164 UHENs and 3221 GRBs was conducted. As a result, 20 GRB-UHEN matches were obtained within a time window of 4 days after the GRBs. Statistical analysis of the results was...
Go to contribution page -
90. Studying the importance of possible oscillations of photons into axion-like particles in pulsarsDr Giorgio Galanti (INAF, Osservatorio Astronomico di Brera)15/04/2021, 08:15
Axion-like particles (ALPs) are hypothetical very light neutral spin-zero bosons predicted by superstring theory which can oscillate into photons in the presence of external magnetic fields. ALPs are attracting increasing interest in the high- and very-high-energy (VHE) astrophysics, since they can explain several issues: they mitigate Universe transparency at VHE, explain why flat spectrum...
Go to contribution page -
Ilias Cholis15/04/2021, 15:00
With gamma-ray observations from Fermi-LAT, cosmic-ray observations from the Alpha Magnetic Spectrometer 02 on board the International Space Station, and with collider data at the LHC and direct detection underground experiments, we are at last probing WIMP dark matter candidates masses and cross-sections. I will discuss the current status of constraints on WIMP scale dark matter from...
Go to contribution page -
Tjark Miener15/04/2021, 15:25
The nature of Dark Matter (DM) is still an open question for modern Physics. In the particle DM paradigm, this elusive kind of matter cannot be made of any of the known particles of the Standard Model (SM) of particle physics. Many efforts have been made in order to model the nature of the DM. Among others, weakly interacting massive particles (WIMPs) are one of the most favored candidates for...
Go to contribution page -
Isabelle Grenier15/04/2021, 15:40
The Galactic Centre region is noteworthy for its massive black hole, bursts of star formation, network of highly magnetised filaments, and bipolar outflow to the halo. This region is of high interest to characterise the nuclei of spiral galaxies and the interstellar medium in starburst galaxies, but its study is hampered by confusion with Galactic activity along the 8.15 kpc-long sightlines to...
Go to contribution page -
Yi Zhang15/04/2021, 16:05
It has been suggested that a huge amount of baryons resides in the circumgalactic medium (CGM) extending out to the virial radii of galaxies. In this work we attempt to measure the baryon mass in CGM with a novel method based on the gamma-ray observations of the extended halo of the Andromeda Galaxy Messier 31 (M31). Since cosmic-ray particles generated inside the galaxy will eventually escape...
Go to contribution page -
Nicola Omodei15/04/2021, 16:35
The Fermi Large Area Telescope (LAT) observations of the active Sun provide the largest sample of solar flares with emission greater than 30 MeV to date. These include detections of impulsive emission coincident with hard X-rays and hours-long sustained emission associated with GOES soft X-ray flares as well as very fast Coronal Mass Ejections (CME). Of particular interest is the first...
Go to contribution page -
Meng Jin15/04/2021, 17:00
With the increasing number of long-duration gamma-ray solar flares >100 MeV observed by Fermi/LAT, it poses a puzzle on the particle acceleration and transport mechanisms. The recent detections of behind-the-limb (BTL) solar flares (e.g., 2014 September 1 event), in which the gamma-ray emission region is located away from the BTL flare site by up to tens of degrees in heliographic longitude,...
Go to contribution page -
15/04/2021, 17:25
-
Warit Mitthumsiri15/04/2021, 17:40
The Earth’s upper atmosphere is constantly bombarded by cosmic rays (CRs). The interactions produce cascades of secondary particles including gamma rays. In any particular region of the upper atmosphere, CRs with insufficient rigidity (momentum per charge) are excluded because they are deflected by the Earth’s magnetic field. Therefore, CR fluxes vary with geographical location, being highest...
Go to contribution page -
Leonardo Di Venere (Universita e INFN, Bari (IT))15/04/2021, 17:55
The asteroid 1I/’Oumuamua (A/2017 U1) and the cometary-like object 2I/Borisov (C/2019 Q4) are the first two objects of interstellar origin discovered in our Solar system. They approached the Earth in October 2017 and in December 2019 respectively.
We searched for gamma-ray emission with the Fermi Large Area Telescope (LAT) data for energies above 56 MeV, focusing on the period before...
Go to contribution page -
Rozeena Ebrahim15/04/2021, 18:10
The Circinus galaxy is a composite starburst/Seyfert galaxy which exhibits radio lobes inflated by kpc scale outflows along its minor axis. Its proximity (4 Mpc) makes it a unique target to study the physical nature of these outflows. We investigate if they originate from nuclear star formation activity or if they are jets from an active galactic core. The MeerKAT radio observations allow us...
Go to contribution page -
Shawaiz Tabassum15/04/2021, 18:10
In the past decade, the most successful approach to search for millisecond pulsars (MSPs) has been to use acceleration searches to look for radio pulsations in the error bars of Gamma-ray sources identified by the Large Area Telescope (LAT) aboard the Fermi Satellite. However, 1000s of gamma-ray sources found by LAT still remain unassociated with any astrophysical object. It is believed that...
Go to contribution page -
Bindu Rani15/04/2021, 18:13
Magnetic reconnection - relinking of magnetic field lines - has been proposed as a possible mechanism to power the high-energy flares in gamma-ray bright Active Galactic Nuclei but has not been confirmed via observations. Our study found observational evidence of magnetic reconnection generated gamma-ray flares in a radio galaxy, 3C 84. In a sequence of radio images, the radio-emitting region...
Go to contribution page -
Pablo Saz Parkinson (The University of Hong Kong)15/04/2021, 18:14
PSR J2021+4026 in the Cygnus region is one of the most interesting radio-quiet pulsars detected by Fermi-LAT. This source, thought to be associated with the Gamma Cygni supernova remnant, is the first isolated gamma-ray pulsar that exhibited clear evidence of variability, with a simultaneous flux and spindown change first occurred in October 2011. After a long recovery phase, in August 2015...
Go to contribution page -
Giacomo Principe15/04/2021, 18:16
According to radiative models, radio galaxies are predicted to produce gamma rays since the first stages of their evolution. The study of the high-energy emission from young radio sources is crucial for providing information on the most energetic processes associated with these sources, the actual region responsible for this emission, as well as the structure of the newly born radio jets....
Go to contribution page -
Tinn Thongmeearkom15/04/2021, 18:18
In the last decade, Fermi LAT has provided an amazing roadmap to assist with pulsar searches conducted in other parts of the electromagnetic system. Indeed, multiple surveys have used Fermi unidentified sources with pulsar-like structures as their targets. Following this strategy, we present in this poster a survey conducted using the MeerKAT telescope to find energetic new pulsars associated...
Go to contribution page -
Zhiyuan Pei15/04/2021, 18:19
In this talk, we will present a two-component model of the γ-ray emission which assumes that the total γ-ray output of blazars consists of relativistically beamed and unbeamed components. 584 Fermi/LAT-blazars are listed in our compiled catalogue. This idea leverages the correlation between the radio core-dominance parameter and the γ-ray beaming factor. We firstly propose a so-called "γ-ray...
Go to contribution page -
Alessia Spolon15/04/2021, 18:22
PSR J0218+4232 is one of the most energetic millisecond pulsars (MSP) known and has been considered as one of the best candidates for very high energy (>100 GeV) γ-ray emission. It has a period of 2.3 ms in a 2-day orbit with a ∼ 0.2M⊙ white dwarf companion. With a characteristic age τ <0.5 Gyr it is one of the youngest MSPs known, with an extremely strong magnetic field at the light cylinder...
Go to contribution page -
Joseph Omojola15/04/2021, 18:22
Phenomenological spectral analysis of S5 1803+784 was done in both the high state and the low state using leptonic jet models. The jet energetic and spectral properties using single zone synchrotron-self Compton (SSC) and SSC with external photons (SSC+EC) jet models are presented. S5 1803+784 is a low synchrotron peak (LSP) blazar with the characteristics weak emission lines
Go to contribution page
(EW < 5A ).... -
Alex McDaniel15/04/2021, 18:25
Many star-forming galaxies and those hosting active galactic nuclei (AGN) show evidence of massive outflows of material in a variety of phases including ionized, neutral atomic, and molecular outflows. Molecular outflows in particular have been the focus of recent interest as they may be responsible for removing gas from the galaxy, thereby suppressing star formation. As the material is...
Go to contribution page -
Elena Orlando15/04/2021, 18:26
Gamma rays from the quiet Sun are produced by Cosmic Rays (CRs) interacting with its surface (disk component) and with its photon field (spatially extended inverse-Compton component, IC). IC is maximum close to the Sun and it extends over the whole sky. Monitoring the IC component with Fermi-LAT allows to obtain information on CR electrons close to the Sun and in the heliosphere for different...
Go to contribution page -
JP Marais15/04/2021, 18:28
The Fermi-LAT has detected more than 5000 gamma-ray sources which show emission above 50 MeV of which 58 per cent belong to the blazar class. However, the Fourth Fermi-LAT catalogue (4FGL) lists 1312 of these as blazar candidates of uncertain type (BCU). Increasing the number of classified Fermi-LAT sources is important for improving our understanding of extra-galactic gamma-ray sources and...
Go to contribution page -
Alex McDaniel15/04/2021, 18:30
Wolf-Rayet (WR) stars are massive evolved stars undergoing advanced nuclear burning in their cores and possess strong stellar winds. WR stars -- and in particular WR binary systems -- are also predicted to be potential emitters of gamma rays. Although details of the high-energy emission mechanisms are not well-understood, a majority of the emission is likely due to strong shocks produced by...
Go to contribution page -
307. Multiwavelength monitoring of gravitationally lensed blazar QSO B0218+357 between 2016 and 2020Francesco Longo15/04/2021, 18:31
QSO B0218+357 is currently the only gravitationally lensed source from which both high-energy (HE, >~100 MeV) and very-high-energy (VHE,>~100GeV) gamma-ray emission has been detected.
We report the Fermi/LAT and multiwavelength monitoring observations of this source in radio interferometry, optical and X-rays performed between 2016 and 2020. During the monitoring, individual flares in the...
Go to contribution page -
David Huber15/04/2021, 18:34
LS 5039 is one of the best-observed gamma-ray binaries with non-thermal emission ranging from soft X-rays to VHE gamma-ray. Explaining the observed anti-correlation between the X-ray/VHE and the HE gamma-ray bands, while accounting for its complex spectral features, has become a challenge for current modelling efforts.
Go to contribution page
We investigate this system in a wind-driven context, where non-thermal... -
Melissa Hallum15/04/2021, 18:34
The quasar 1156+295 (4C 29.45, Ton599) underwent a dramatic nonthermal outburst in late 2017, with detection at energies > 100 GeV. The outburst was essentially simultaneous at gamma-ray and optical bands, indicating co-spatiality of the emission regions. We present multi-epoch optical spectra of 1156+295 obtained with the 4.3 m Lowell Discovery Telescope at various times, including the...
Go to contribution page -
Graziano Chiaro15/04/2021, 18:37
Radio-loud sources with blazar-like properties, but having a jet that does not directly point in the direction of the observer are among the most interesting classes of gamma-ray emitters. These sources are known as Misaligned Active Galactic Nuclei (MAGN). We searched for new MAGN candidates among the remaining blazars of uncertain type detected by the Fermi Large Area Telescope (LAT) using a...
Go to contribution page -
Raniere Menezes (Universidade de São Paulo)15/04/2021, 18:38
The gamma-ray emission from stars is induced by the interaction of cosmic rays with stellar atmospheres and photon fields. This emission is expected to come in two components: a stellar disk emission, where gamma-rays are mainly produced in atmospheric showers generated by hadronic cosmic rays, and an extended halo emission, where the high density of soft photons in the surroundings of stars...
Go to contribution page -
Marco Ajello15/04/2021, 18:40
Massive black holes at the centers of galaxies can launch powerful wide-angle winds, which if sustained over time can unbind the gas from the stellar bulges of galaxies. Propagating through the galaxy, the wind should interact with the interstellar medium creating a strong shock, similar to those observed in supernovae explosions, which is able to accelerate charged particles to high...
Go to contribution page -
Robin Corbet15/04/2021, 18:42
Superorbital periods in Roche-lobe overflowing X-ray binaries such as Her X-1 have been known for some time. These can be understood as being related to the presence of an accretion disk. However, more recently a number of HMXBs accreting from the wind of their supergiant companion, where the presence of a persistent accretion disk is unlikely, have also been found to show superorbital...
Go to contribution page -
Natalia Zywucka15/04/2021, 18:43
We present the results of a preliminary investigation of a potential association of a blazar
Go to contribution page
candidate behind the Large Magellanic Cloud (LMC) and a gamma-ray transient object.
The hint of flaring activity appeared at the position (RA,dec)∼(86.60 deg,-69.02 deg), while
the J0545-6846 blazar candidate is located at (RA,dec)=(86.47 deg,-68.77 deg). J0545-6846 is characterised by a... -
Colin Clark15/04/2021, 18:46
The ability of the Fermi Large Area Telescope to identify pulsar-like gamma-ray sources has sparked a huge increase in discoveries of "Spider" millisecond pulsar binaries (Black Widows and Redbacks). These systems are characterised by long radio eclipses due to scattering and absorption by diffuse intra-binary material that has been evaporated from the companion star's surface. Unlike radio...
Go to contribution page -
Zacharias Michael15/04/2021, 18:46
The FSRQ CTA 102 (z=1.032) has been tremendously active over the last few years. During its peak activity lasting several months in late 2016 and early 2017, the gamma-ray and optical fluxes rose by up to a factor 100 above the quiescence level. We have interpreted the peak activity as the ablation of a gas cloud by the relativistic jet, which can nicely account for the months-long lightcurve...
Go to contribution page -
Jacobus van den Berg15/04/2021, 18:49
We test different physically motivated models for the spectral shape of the gamma-ray emission in a sample of 128 blazars with known redshifts detected by Fermi-LAT at energies above 50 GeV. The first nine years of LAT data in the energy range from 300 MeV to 2 TeV are analyzed in order to extend the spectral energy coverage of the 2FHL blazars in our sample. We compare these spectral data to...
Go to contribution page -
Robert Brose15/04/2021, 18:50
Supernova remnants are known to accelerate cosmic rays on account of their non-thermal emission of radio waves, X-rays, and gamma rays. However, the ability to accelerate cosmic-rays up to PeV-energies has yet to be demonstrated. The presence of cut-offs in the gamma-ray spectra of several young SNRs led to the idea that PeV-energies might only be achieved during the very initial stages of a...
Go to contribution page -
Hannes Thiersen15/04/2021, 18:52
Most research on blazar variability focuses on individual flares to explain acceleration
Go to contribution page
and radiation mechanisms and improve on current models. These short-time events
(being minutes, hours, or days) might not be representative of the underlying mecha-
nisms causing small-amplitude variability and/or continuous emission which is present
most of the time. We will therefore investigate... -
Robert Brose15/04/2021, 18:54
Supernova remnants are known to accelerate particles to relativistic energies on account of their non-thermal emission. The observational progress from radio to gamma-ray observations reveals more and more morphological features that need to be accounted for when modeling the emission from those objects.
Go to contribution page
We use our time-dependent acceleration code RATPaC to study the formation of extended... -
Mithun Randu15/04/2021, 18:55
An active galactic nucleus with a relativistic jet pointing within 10o of the line of the sight of the earth is known as a Blazar. Normally a Blazar has two relativistic jets. These jets are linear features instigating very close to the super massive black hole (SMBH) at the center of an Active Galactic Nucleus (AGN). A broad region of energies consist in these jets from radio rays to gamma...
Go to contribution page -
Anabella Araudo15/04/2021, 18:58
Synchrotron radio emission from non-relativistic jets powered by massive protostars has been reported, indicating the presence of relativistic electrons and mG magnetic fields. We study diffusive shock acceleration and magnetic field amplification in protostellar jets with speeds between 300 and 1000 km/s. We show that the magnetic field in the synchrotron emitter can be amplified by the...
Go to contribution page -
Laenita Oberholzer15/04/2021, 18:58
On the 28th of January, an orphan very-high-energy γ-ray flare from 3C279
Go to contribution page
was detected, not accompanied by flaring in the adjacent GeV gamma-ray
regime. Orphan flares have to be caused by different processes than normal
γ-ray flares. Specifically, the Hadronic Synchrotron Mirror Model has been
proposed to provide a consistent explanation of this flare. The expected tar-
get photon... -
Nomthendeleko Motha15/04/2021, 19:01
The extragalactic radio background in the universe is mainly due to emission from the radio galaxies and normal galaxies. This emission is synchrotron radiation by relativistic electrons gyrating in the magnetic field of the galaxies. Synchrotron self-absorption and free-free absorptions by hot ionised gas in the interstellar medium play an important role to modify radio emission. In this...
Go to contribution page -
Iurii Sushch (Deutsches Elektronen-Synchrotron DESY)15/04/2021, 19:02
Supernova remnants (SNRs) are widely believed to be one of the main candidates for the origin of Galactic cosmic rays. Very-high-energy gamma-ray emission observed from a number of SNRs suggests that particles are indeed accelerated to high energies by shock in remnants. However, it is extremely difficult to discriminate which particles are responsible for this emission as both protons...
Go to contribution page -
Andrea Gokus15/04/2021, 19:04
While blazars are abundant in the gamma-ray sky, there is only a handful of narrow-line Seyfert 1 galaxies that Fermi/LAT detected in more than 10 years of observation. Flares from this elusive source class are among the rarest events that Fermi has seen so far.
Go to contribution page
One of them is the radio- and gamma-ray loud source PKS 2004-447. It exhibits blazar-like features, i.e., a flat featureless X-ray... -
Drikus Plooy15/04/2021, 19:06
Gamma-ray binaries are a class of high-mass binary systems which are distinguished by their spectral energy distributions peaking above 1 MeV. Gamma-ray binaries consist of an O or B type companion and an orbiting compact object which is either a neutron star or a black hole. Generally in these systems the nature of the compact object is unknown except for two cases, namely PSR B1259-63 and...
Go to contribution page -
Yasushi Fukazawa15/04/2021, 19:07
FSRQs are important to study cosmic evolution of AGN jet and also interesting how they contribute to the cosmic MeV gamma-ray background. Past studies with hard X-ray (Swift/BAT 22 month catalog) and GeV gamma-ray (Fermi/LAT) reported the X-ray and gamma-ray luminosity function, but predicts a different evolution between X-ray and GeV gamma-ray. Here we used the Swift/BAT 105 month catalog to...
Go to contribution page -
Constantinos Kalapotharakos (UMCP CRESST / NASA GSFC)15/04/2021, 19:10
The Fermi data imply that the gamma-ray observables, i.e., the gamma-ray luminosity, spectral cut-off energy, stellar surface magnetic field, and spin-down power obey a relation that represents a 3D plane in the 4D log-space. This observed fundamental plane (FP) is remarkably close to the theoretical relation that is obtained, assuming that the pulsar gamma-ray emission is due to curvature...
Go to contribution page -
Saikat Das15/04/2021, 19:10
We explain the observed multiwavelength photon spectrum of some high energy BL Lac objects, using a lepto-hadronic model. The one-zone leptonic emission is employed to fit the synchrotron peak. Subsequently, the SSC spectrum is calculated, such that it extends up to the highest energy possible for the jet parameters considered. The data points beyond this and also in the entire VHE range (E>30...
Go to contribution page -
Brandon Bisschoff15/04/2021, 19:13
Galaxies and galaxy clusters are separated by large distances of nearly empty
Go to contribution page
space called the intergalactic space. In these large, nearly empty regions a weak magnetic field of strength < 10 nG is present that is predicted to be of primordial (early universe) origin. This is called the intergalactic magnetic field (IGMF) and knowledge about its strength, coherence length, origin etc. is... -
Maria Edvige Ravasio16/04/2021, 07:00
I will present the interesting case of GRB 190114C, the first GRB ever detected by MAGIC at Very High Energy (VHE). We analyzed the spectral evolution of its gamma-ray emission as detected by the Fermi Gamma-Ray Burst Monitor (GBM) up to∼60 s. We revealed the presence of an extra component starting on ∼4 s post-trigger. This extra component rises and decays quickly (peaking at∼6 s) and it is...
Go to contribution page -
Shawaiz Tabassum16/04/2021, 07:00
In the past decade, the most successful approach to search for millisecond pulsars (MSPs) has been to use acceleration searches to look for radio pulsations in the error bars of Gamma-ray sources identified by the Large Area Telescope (LAT) aboard the Fermi Satellite. However, 1000s of gamma-ray sources found by LAT still remain unassociated with any astrophysical object. It is believed that...
Go to contribution page -
Pieter van der Merwe16/04/2021, 07:04
In 2015 the advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO) detected the first ever gravitational event, gravitational wave event GW150914, with multiple new gravitational wave events, originating from both binary neutron stars and binary black hole (BBH) mergers, detected in subsequent years. In light of these detections, we simulate the dynamics of ambient test particles...
Go to contribution page -
Pablo Saz Parkinson (The University of Hong Kong)16/04/2021, 07:05
PSR J2021+4026 in the Cygnus region is one of the most interesting radio-quiet pulsars detected by Fermi-LAT. This source, thought to be associated with the Gamma Cygni supernova remnant, is the first isolated gamma-ray pulsar that exhibited clear evidence of variability, with a simultaneous flux and spindown change first occurred in October 2011. After a long recovery phase, in August 2015...
Go to contribution page -
Mariusz Tarnopolski16/04/2021, 07:08
Two classes of gamma-ray bursts (GRBs), short and long, have been confidently identified thus far and are prescribed to different physical scenarios. A third class, intermediate in duration, was suggested to be present in various catalogues based on a mixture-modelling with two or three Gaussian distributions of the log-durations, log(T90). This might not be an adequate model. An analysis of...
Go to contribution page -
Tinn Thongmeearkom16/04/2021, 07:10
In the last decade, Fermi LAT has provided an amazing roadmap to assist with pulsar searches conducted in other parts of the electromagnetic system. Indeed, multiple surveys have used Fermi unidentified sources with pulsar-like structures as their targets. Following this strategy, we present in this poster a survey conducted using the MeerKAT telescope to find energetic new pulsars associated...
Go to contribution page -
Saeeda Sajjad16/04/2021, 07:12
The second Fermi LAT GRB catalog presents the results for 186 Gamma Ray Bursts (GRBs) detected by the Fermi Large Area Telescope (LAT) between 2008 and 2018. Out of these, we select the GRBs with significant detection in the LAT and GBM during the T90 time interval. We further subdivide this population into four quartiles based on the fluence from the GBM and carry out joint GBM-LAT spectral...
Go to contribution page -
Alessia Spolon16/04/2021, 07:15
PSR J0218+4232 is one of the most energetic millisecond pulsars (MSP) known and has been considered as one of the best candidates for very high energy (>100 GeV) γ-ray emission. It has a period of 2.3 ms in a 2-day orbit with a ∼ 0.2M⊙ white dwarf companion. With a characteristic age τ <0.5 Gyr it is one of the youngest MSPs known, with an extremely strong magnetic field at the light cylinder...
Go to contribution page -
Alessandro Carosi, Alicia Lopez, Francesco Longo16/04/2021, 07:16
The Cherenkov Telescope Array (CTA) will be the next generation very high-energy (VHE) gamma-ray observatory. It will improve the sensitivity of current VHE instruments up to an order of magnitude and will cover the energy range from 20 GeV to at least 300 TeV. With its sensitivity, it will explore high redshift sources and extreme accelerators and will give access to the shortest timescale...
Go to contribution page -
Rahul Gupta16/04/2021, 07:20
We present the results of a detailed investigation of the prompt and afterglow emission in the High Energy Stereoscopic System(H.E.S.S.)-detected GRB190829A. Swift and Fermi observations of the prompt phase of this gamma-ray burst(GRB) reveal two isolated sub bursts or episodes, separated by a quiescent phase. The energetic and the spectral properties of the first episode are in stark contrast...
Go to contribution page -
Elena Orlando16/04/2021, 07:20
Gamma rays from the quiet Sun are produced by Cosmic Rays (CRs) interacting with its surface (disk component) and with its photon field (spatially extended inverse-Compton component, IC). IC is maximum close to the Sun and it extends over the whole sky. Monitoring the IC component with Fermi-LAT allows to obtain information on CR electrons close to the Sun and in the heliosphere for different...
Go to contribution page -
Daniela Dorner16/04/2021, 07:24
Operational since October 2011, the First G-APD Cherenkov Telescope
Go to contribution page
(FACT) has been monitoring TeV-blazars. An unbiased observing strategy,
robotic operation and the usage of solid state photo sensors (SiPM, aka
G-APDs) increase the instrument's duty cycle and minimize observational
gaps, making FACT an ideal instrument for long-term monitoring. In more
than eight years, an unprecedented... -
Alex McDaniel16/04/2021, 07:25
Wolf-Rayet (WR) stars are massive evolved stars undergoing advanced nuclear burning in their cores and possess strong stellar winds. WR stars -- and in particular WR binary systems -- are also predicted to be potential emitters of gamma rays. Although details of the high-energy emission mechanisms are not well-understood, a majority of the emission is likely due to strong shocks produced by...
Go to contribution page -
Peter Veres16/04/2021, 07:28
We present the observations of the first unambiguous magnetar giant flare from outside of our galactic neighborhood. At the beginning, GRB 200415A was identified as a short GRB, but upon further investigation and observations from additional instruments, we concluded this event was a giant flare from a magnetar located in the Sculptor galaxy, 3.5 Mpc away. The GBM lightcurve shows very fast...
Go to contribution page -
David Huber16/04/2021, 07:30
LS 5039 is one of the best-observed gamma-ray binaries with non-thermal emission ranging from soft X-rays to VHE gamma-ray. Explaining the observed anti-correlation between the X-ray/VHE and the HE gamma-ray bands, while accounting for its complex spectral features, has become a challenge for current modelling efforts.
Go to contribution page
We investigate this system in a wind-driven context, where non-thermal... -
Vidushi Sharma16/04/2021, 07:32
The nature of the gamma-ray burst (GRB) central engine remains an enigma. Entities widely considered to be capable of powering the extreme jets are: (i) a hyper-accreting stellar-mass black hole, and (ii) a rapidly spinning, highly magnetized, neutron star (NS) or fast magnetar. The maximum rotational energy that is feasible in a millisecond magnetar to form a jet is ~10^52 erg and hence...
Go to contribution page -
Raniere Menezes (Universidade de São Paulo)16/04/2021, 07:35
The gamma-ray emission from stars is induced by the interaction of cosmic rays with stellar atmospheres and photon fields. This emission is expected to come in two components: a stellar disk emission, where gamma-rays are mainly produced in atmospheric showers generated by hadronic cosmic rays, and an extended halo emission, where the high density of soft photons in the surroundings of stars...
Go to contribution page -
Samuele Ronchini (Gran Sasso Science Institute)16/04/2021, 07:36
γ-ray bursts (GRBs) are cataclysmic events, whose role became central in the new multi-messenger era. GRBs are thought to originate from internal dissipation of the energy carried by ultra-relativistic jets launched by the remnant of a massive star’s death or a compact binary coalescence. In the present work I propose a novel investigation of the GRB emission mechanism, via time-resolved...
Go to contribution page -
Antonios Nathanail16/04/2021, 07:40
We perform three-dimensional (3D) general-relativistic magnetohydrodynamic sim-
Go to contribution page
ulations to model the jet break-out from the ejecta expected to be produced in a
binary neutron-star merger. The structure of the relativistic outflow from the 3D sim-
ulation confirms our previous results from 2D simulations, namely, that a relativistic
magnetized outflow breaking out from the merger ejecta... -
Robin Corbet16/04/2021, 07:40
Superorbital periods in Roche-lobe overflowing X-ray binaries such as Her X-1 have been known for some time. These can be understood as being related to the presence of an accretion disk. However, more recently a number of HMXBs accreting from the wind of their supergiant companion, where the presence of a persistent accretion disk is unlikely, have also been found to show superorbital...
Go to contribution page -
Daniel Kerszberg (IFAE - Institute for High Energy Physics)16/04/2021, 07:44
On January 14th 2019, MAGIC, a stereoscopic system of two 17m diameter Imaging Atmospheric Cherenkov Telescopes located on the Canary island of La Palma, observed for the first time a gamma-ray burst (GRB) at TeV energies, namely GRB 190114C. MAGIC measurements started ~60s after the onset of GRB 190114C, predominantly in the featureless smooth afterglow phase. Nevertheless, in the first 30s...
Go to contribution page -
Colin Clark16/04/2021, 07:45
The ability of the Fermi Large Area Telescope to identify pulsar-like gamma-ray sources has sparked a huge increase in discoveries of "Spider" millisecond pulsar binaries (Black Widows and Redbacks). These systems are characterised by long radio eclipses due to scattering and absorption by diffuse intra-binary material that has been evaporated from the companion star's surface. Unlike radio...
Go to contribution page -
Tynik Idrissova16/04/2021, 07:48
For research, our group uses an installation with an area of 55 m2, consisting of two recording levels, gamma and hadron blocks, separated by a two-meter gap, located at the Tien Shan high-altitude scientific station. The main idea is to select interactions that are only observed in the gamma block, and not observed in the hadron block.
Go to contribution page
The upgraded ionization calorimeter with a field of... -
Robert Brose16/04/2021, 07:50
Supernova remnants are known to accelerate cosmic rays on account of their non-thermal emission of radio waves, X-rays, and gamma rays. However, the ability to accelerate cosmic-rays up to PeV-energies has yet to be demonstrated. The presence of cut-offs in the gamma-ray spectra of several young SNRs led to the idea that PeV-energies might only be achieved during the very initial stages of a...
Go to contribution page -
Sylvain Guiriec (NASA Goddard Space Flight Center / UMD / CRESST)16/04/2021, 07:52
Over the past few years, evidence has been accumulated in support of the existence of a thermal-like component during the GRB prompt phase. This component--often associated with the GRB jet's photosphere--is usually subdominant compared to a much stronger non-thermal one. The prompt emission of GRB 131014A detected by Fermi provides a unique opportunity to trace the history of this...
Go to contribution page -
Robert Brose16/04/2021, 07:55
Supernova remnants are known to accelerate particles to relativistic energies on account of their non-thermal emission. The observational progress from radio to gamma-ray observations reveals more and more morphological features that need to be accounted for when modeling the emission from those objects.
Go to contribution page
We use our time-dependent acceleration code RATPaC to study the formation of extended... -
Shashi Bhushan Pandey16/04/2021, 07:56
TeV emissions from Gamma-ray bursts (GRBs) are very important to study the origin and the radiation mechanisms in detail. Recent discoveries of TeV photons in some of the GRBs are challenging to be explained by Synchrotron mechanism. In this work, we present the results of a detailed investigation of the prompt and afterglow emission of recently discovered TeV GRBs (GRB 180720B, GRB 190114C...
Go to contribution page -
Anabella Araudo16/04/2021, 08:00
Synchrotron radio emission from non-relativistic jets powered by massive protostars has been reported, indicating the presence of relativistic electrons and mG magnetic fields. We study diffusive shock acceleration and magnetic field amplification in protostellar jets with speeds between 300 and 1000 km/s. We show that the magnetic field in the synchrotron emitter can be amplified by the...
Go to contribution page -
Amit Kumar16/04/2021, 08:00
This poster presents data and analysis of SN 2010kd, a low-redshift (z = 0.101) H-deficient superluminous supernova (SLSN), based on ultraviolet/optical photometry and optical spectroscopy spanning between −28 and +193 days relative to B band maximum light. The B band light curve comparison of SN 2010kd with a subset of well-studied SLSNe at comparable redshifts indicates that it is a...
Go to contribution page -
Daniela Dorner16/04/2021, 08:04
Blazars are extremely variable sources showing flux variations on time scales from minutes to years. To study typical variability time scales of few hours to one day, continuous observations are crucial. Furthermore, studying the temporal evolution of the spectral energy distribution is a key to discriminate between different theoretical models for the emission mechanisms and processes...
Go to contribution page -
Iurii Sushch (Deutsches Elektronen-Synchrotron DESY)16/04/2021, 08:05
Supernova remnants (SNRs) are widely believed to be one of the main candidates for the origin of Galactic cosmic rays. Very-high-energy gamma-ray emission observed from a number of SNRs suggests that particles are indeed accelerated to high energies by shock in remnants. However, it is extremely difficult to discriminate which particles are responsible for this emission as both protons...
Go to contribution page -
Antonio de Ugarte Postigo16/04/2021, 08:08
GRB 171205A was one of the closest GRBs that we have ever detected and one of the best-followed events. In this talk I will present the result of several studies of this event, its afterglow, associated supernova SN2017iuk, and host galaxy. Optical spectroscopy ranges from one hour after the event to more than 7 months later. These data served to identify cocoon signatures during the first 3...
Go to contribution page -
Drikus Plooy16/04/2021, 08:10
Gamma-ray binaries are a class of high-mass binary systems which are distinguished by their spectral energy distributions peaking above 1 MeV. Gamma-ray binaries consist of an O or B type companion and an orbiting compact object which is either a neutron star or a black hole. Generally in these systems the nature of the compact object is unknown except for two cases, namely PSR B1259-63 and...
Go to contribution page -
Amar Aryan16/04/2021, 08:12
In this paper,we present the observed photo metric and spectroscopic properties of a
Go to contribution page
type Ib supernova (SN) SN2015ap. Our aim in this paper is to model a reliable progenitor for SN2015ap, which can undergo core-collapse and explain the observed properties
of this SN. Initially, this SN shows some broad-lined features like SN2008D and later
it shows features matching with normal type Ib... -
Constantinos Kalapotharakos (UMCP CRESST / NASA GSFC)16/04/2021, 08:15
The Fermi data imply that the gamma-ray observables, i.e., the gamma-ray luminosity, spectral cut-off energy, stellar surface magnetic field, and spin-down power obey a relation that represents a 3D plane in the 4D log-space. This observed fundamental plane (FP) is remarkably close to the theoretical relation that is obtained, assuming that the pulsar gamma-ray emission is due to curvature...
Go to contribution page -
José Feliciano Agüí Fernández16/04/2021, 08:16
Short gamma-ray burst are, as we now know, produced as the result of the coalescence of two compact objects. These objects are also known to release large amounts of energy in gravitational waves during the merger. We present our first results on the study of GRB 160410A, an undoubtedly short GRB at z=1.717, making it one of the farthest short GRBs to date. We observed the afterglow emission...
Go to contribution page -
Nukri Komin (Wits University)16/04/2021, 15:00
The High Energy Stereoscopic System (H.E.S.S.) has conducted a survey of the Milky Way, discovering 78 sources of very-high-energy (VHE, E > 100 GeV) gamma-ray emission. A total of 28 sources are firmly identified as being Pulsar Wind Nebulae (PWNe), Supernova Remnants (SNRs) or composite SNRs. Correlating the H.E.S.S. sources with other catalogues shows that 21 objects are firmly or plausibly...
Go to contribution page -
Christo Venter (North-West University Potchefstroom Campus)16/04/2021, 15:25
The Fermi Large Area Telescope (LAT) has caused a revolution in the field of high-energy pulsar science. The number of known pulsars has sky-rocketed from a mere handful prior to its launch to more than 250, and the accumulation of statistics has yielded superior quality light curves in some cases. These developments have stimulated and enabled a flurry of theoretical activity, substantially...
Go to contribution page -
Matthew Kerr16/04/2021, 15:50
The Third Fermi Pulsar Catalog (3PC) is nearing completion and will provide timing solutions, pulse profiles, spectra, and ancillary data for about 250 gamma-ray detected pulsars. It is a tremendous undertaking, as it continues the geometric increase in source count established by 1PC (46 pulsars) and 2PC (117 pulsars). This large population reflects the application of...
Go to contribution page -
16/04/2021, 16:05
-
Peter Predehl16/04/2021, 16:35
-
Russ Taylor16/04/2021, 17:00
The first decades of this century has seen a tremendous advance in information and digital technologies impacting scientific inquiry. Data being created by global projects in science and engineering, by the ubiquitous sensors tracking the state of the planet, by the connected internet of things, and by vast and complex collections of meta data that trace the patterns and trends in human...
Go to contribution page -
Jamie Holder (University of Delaware)16/04/2021, 17:25
The Cherenkov Telescope Array (CTA) is a next generation facility for ground-based gamma-ray astronomy operating in the very high energy (20 GeV to 300 TeV) range. It will consist of two telescope arrays, one on the island of La Palma in the Canary Islands, and the other near Paranal, Chile. CTA will provide order of magnitude improvements in sensitivity over current instrunments, together...
Go to contribution page -
Dr Michael Backes (University of Namibia)16/04/2021, 17:50
Astronomy plays a major role in the scientific landscape of Namibia and Southern Africa. Considerable progress has been achieved scientifically as well as in terms of human capacity development in the field. In all wavelength regimes accessible with ground-based instruments, the largest of those instruments are situated in Southern Africa: MeerKAT, the Southern African Large Telescope, and the...
Go to contribution page -
Alisha Chromey16/04/2021, 18:05
VERITAS (Very Energetic Radiation Imaging Telescope Array System) is one of the world’s most sensitive very-high-energy (VHE; E > 100 GeV) gamma-ray detectors. It consists of four 12-m imaging atmospheric Cherenkov telescopes and has been operating continuously in a full-array mode since 2007. In fourteen years of operation, VERITAS has made a remarkable contribution to the development of...
Go to contribution page -
Brandon Bisschoff16/04/2021, 18:20
Galaxies and galaxy clusters are separated by large distances of nearly empty
Go to contribution page
space called the intergalactic space. In these large, nearly empty regions a weak magnetic field of strength < 10 nG is present that is predicted to be of primordial (early universe) origin. This is called the intergalactic magnetic field (IGMF) and knowledge about its strength, coherence length, origin etc. is... -
Isabella Mereu16/04/2021, 18:20
Gamma-ray catalogs produced with data of the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope typically integrate years of exposure. Since Active Galactic Nuclei (AGNs) are characterized by strong and fast variability, their emission is diluted by long-time data integration. Transient sources can be more easily detected over short time scales. In order to search for...
Go to contribution page -
Saikat Das16/04/2021, 18:26
We explain the observed multiwavelength photon spectrum of some high energy BL Lac objects, using a lepto-hadronic model. The one-zone leptonic emission is employed to fit the synchrotron peak. Subsequently, the SSC spectrum is calculated, such that it extends up to the highest energy possible for the jet parameters considered. The data points beyond this and also in the entire VHE range (E>30...
Go to contribution page -
Naomi Tsuji16/04/2021, 18:27
We report the results of cross-match between the hard X-ray and GeV gamma-ray catalogs, by making use of the latest 105-month Swift/BAT and 10-yr Fermi/LAT catalogs, respectively. We found 181 matched sources in total, which include 36 of false-match, unidentified, and ambiguous sources. The firmly matched sources consist of blazars (> 60%), pulsars and pulsar wind nebulae (∼10%), radio...
Go to contribution page -
Yasushi Fukazawa16/04/2021, 18:29
FSRQs are important to study cosmic evolution of AGN jet and also interesting how they contribute to the cosmic MeV gamma-ray background. Past studies with hard X-ray (Swift/BAT 22 month catalog) and GeV gamma-ray (Fermi/LAT) reported the X-ray and gamma-ray luminosity function, but predicts a different evolution between X-ray and GeV gamma-ray. Here we used the Swift/BAT 105 month catalog to...
Go to contribution page -
Andrea Gokus16/04/2021, 18:32
While blazars are abundant in the gamma-ray sky, there is only a handful of narrow-line Seyfert 1 galaxies that Fermi/LAT detected in more than 10 years of observation. Flares from this elusive source class are among the rarest events that Fermi has seen so far.
Go to contribution page
One of them is the radio- and gamma-ray loud source PKS 2004-447. It exhibits blazar-like features, i.e., a flat featureless X-ray... -
Elena Orlando16/04/2021, 18:34
The Fermi Large Area Telescope (LAT) has been detecting hundreds of Galactic sources, most of which are pulsars. Many Galactic sources are still undetected or unresolved due to their low flux, below the Fermi LAT sensitivity, or because of foreground and source confusion. Moreover, among the many unassociated sources, which are one third of the detected sources, a large amount may have...
Go to contribution page -
Nomthendeleko Motha16/04/2021, 18:35
The extragalactic radio background in the universe is mainly due to emission from the radio galaxies and normal galaxies. This emission is synchrotron radiation by relativistic electrons gyrating in the magnetic field of the galaxies. Synchrotron self-absorption and free-free absorptions by hot ionised gas in the interstellar medium play an important role to modify radio emission. In this...
Go to contribution page -
Laenita Oberholzer16/04/2021, 18:38
On the 28th of January, an orphan very-high-energy γ-ray flare from 3C279
Go to contribution page
was detected, not accompanied by flaring in the adjacent GeV gamma-ray
regime. Orphan flares have to be caused by different processes than normal
γ-ray flares. Specifically, the Hadronic Synchrotron Mirror Model has been
proposed to provide a consistent explanation of this flare. The expected tar-
get photon... -
Luca Giunti16/04/2021, 18:41
The identification of active PeVatrons, hadronic particle accelerators reaching the knee (at the energy of few PeV), is crucial to understand the origin of cosmic rays in the Galaxy. In this context, we report on new H.E.S.S. observations of the PeVatron candidate HESSJ1702-420, close to the source 2FHL J1703.4-4145, that have revealed the presence of gamma-rays up to 100 TeV at 5 sigma...
Go to contribution page -
Mithun Randu16/04/2021, 18:41
An active galactic nucleus with a relativistic jet pointing within 10o of the line of the sight of the earth is known as a Blazar. Normally a Blazar has two relativistic jets. These jets are linear features instigating very close to the super massive black hole (SMBH) at the center of an Active Galactic Nucleus (AGN). A broad region of energies consist in these jets from radio rays to gamma...
Go to contribution page -
Hannes Thiersen16/04/2021, 18:44
Most research on blazar variability focuses on individual flares to explain acceleration
Go to contribution page
and radiation mechanisms and improve on current models. These short-time events
(being minutes, hours, or days) might not be representative of the underlying mecha-
nisms causing small-amplitude variability and/or continuous emission which is present
most of the time. We will therefore investigate... -
Jacobus van den Berg16/04/2021, 18:47
We test different physically motivated models for the spectral shape of the gamma-ray emission in a sample of 128 blazars with known redshifts detected by Fermi-LAT at energies above 50 GeV. The first nine years of LAT data in the energy range from 300 MeV to 2 TeV are analyzed in order to extend the spectral energy coverage of the 2FHL blazars in our sample. We compare these spectral data to...
Go to contribution page -
Alejandra Aguirre-Santaella16/04/2021, 18:48
TeV DM candidates are gradually earning more and more attention within the community. Among others, extra-dimensional brane-world models may produce thermal DM candidates with masses up to 100 TeV, which could be detected with the next generation of very-high-energy gamma-ray observatories such as the Cherenkov Telescope Array (CTA).
Go to contribution page
In this work, we study the sensitivity of CTA to branon DM... -
Zacharias Michael16/04/2021, 18:50
The FSRQ CTA 102 (z=1.032) has been tremendously active over the last few years. During its peak activity lasting several months in late 2016 and early 2017, the gamma-ray and optical fluxes rose by up to a factor 100 above the quiescence level. We have interpreted the peak activity as the ablation of a gas cloud by the relativistic jet, which can nicely account for the months-long lightcurve...
Go to contribution page -
Natalia Zywucka16/04/2021, 18:53
We present the results of a preliminary investigation of a potential association of a blazar
Go to contribution page
candidate behind the Large Magellanic Cloud (LMC) and a gamma-ray transient object.
The hint of flaring activity appeared at the position (RA,dec)∼(86.60 deg,-69.02 deg), while
the J0545-6846 blazar candidate is located at (RA,dec)=(86.47 deg,-68.77 deg). J0545-6846 is characterised by a... -
Jeremy Hare16/04/2021, 18:55
The release of the Fermi-LAT 4FGL catalog includes over 1,000 unidentified Fermi-LAT sources (roughly 25% of sources). One of the most successful ways to uncover their counterparts are through X-ray observations. Over their ~20 year lifetimes XMM-Newton and Chandra have observed a large number of Galactic fields, many of which contain unidentified Galactic Fermi-LAT sources. Often these fields...
Go to contribution page -
Marco Ajello16/04/2021, 18:56
Massive black holes at the centers of galaxies can launch powerful wide-angle winds, which if sustained over time can unbind the gas from the stellar bulges of galaxies. Propagating through the galaxy, the wind should interact with the interstellar medium creating a strong shock, similar to those observed in supernovae explosions, which is able to accelerate charged particles to high...
Go to contribution page -
Graziano Chiaro16/04/2021, 18:59
Radio-loud sources with blazar-like properties, but having a jet that does not directly point in the direction of the observer are among the most interesting classes of gamma-ray emitters. These sources are known as Misaligned Active Galactic Nuclei (MAGN). We searched for new MAGN candidates among the remaining blazars of uncertain type detected by the Fermi Large Area Telescope (LAT) using a...
Go to contribution page -
Geoff Beck16/04/2021, 19:02
Gamma-ray probes have historically been a gold-standard in indirect dark matter detection due to their smaller set of complicating factors and generally lower backgrounds. However, they are most optimally sensitive to the traditional supersymmetric WIMP annihilation channels and leptophilic channels (particularly for larger masses) are much harder to probe effectively in this manner. However,...
Go to contribution page -
Melissa Hallum16/04/2021, 19:02
The quasar 1156+295 (4C 29.45, Ton599) underwent a dramatic nonthermal outburst in late 2017, with detection at energies > 100 GeV. The outburst was essentially simultaneous at gamma-ray and optical bands, indicating co-spatiality of the emission regions. We present multi-epoch optical spectra of 1156+295 obtained with the 4.3 m Lowell Discovery Telescope at various times, including the...
Go to contribution page -
330. Multiwavelength monitoring of gravitationally lensed blazar QSO B0218+357 between 2016 and 2020Francesco Longo16/04/2021, 19:05
QSO B0218+357 is currently the only gravitationally lensed source from which both high-energy (HE, >~100 MeV) and very-high-energy (VHE,>~100GeV) gamma-ray emission has been detected.
We report the Fermi/LAT and multiwavelength monitoring observations of this source in radio interferometry, optical and X-rays performed between 2016 and 2020. During the monitoring, individual flares in the...
Go to contribution page -
JP Marais16/04/2021, 19:08
The Fermi-LAT has detected more than 5000 gamma-ray sources which show emission above 50 MeV of which 58 per cent belong to the blazar class. However, the Fourth Fermi-LAT catalogue (4FGL) lists 1312 of these as blazar candidates of uncertain type (BCU). Increasing the number of classified Fermi-LAT sources is important for improving our understanding of extra-galactic gamma-ray sources and...
Go to contribution page -
Pablo Saz Parkinson (The University of Hong Kong)16/04/2021, 19:09
The Fermi LAT Fourth Source Catalog (4FGL) contains over 5000 gamma-ray sources detected using 8 years of LAT data. Among these sources, over 3000 are associated with known blazars, 239 are associated with pulsars, and over 1300 are classified as 'unassociated' sources, meaning they have no known plausible counterpart at any other wavelength. Following on our previous work on the 3FGL Catalog...
Go to contribution page -
Alex McDaniel16/04/2021, 19:11
Many star-forming galaxies and those hosting active galactic nuclei (AGN) show evidence of massive outflows of material in a variety of phases including ionized, neutral atomic, and molecular outflows. Molecular outflows in particular have been the focus of recent interest as they may be responsible for removing gas from the galaxy, thereby suppressing star formation. As the material is...
Go to contribution page -
Joseph Omojola16/04/2021, 19:14
Phenomenological spectral analysis of S5 1803+784 was done in both the high state and the low state using leptonic jet models. The jet energetic and spectral properties using single zone synchrotron-self Compton (SSC) and SSC with external photons (SSC+EC) jet models are presented. S5 1803+784 is a low synchrotron peak (LSP) blazar with the characteristics weak emission lines
Go to contribution page
(EW < 5A ).... -
Michael Sarkis16/04/2021, 19:16
Recent studies of the effects on the Earth’s atmosphere by astrophysical sources, such as nearby gamma-ray bursts or supernovae, have shown that these events could lead to severe changes in atmospheric composition. Depletion of ozone, the most notable of these changes, is extremely dangerous to living organisms as any decrease in ozone levels leads to an increase in the irradiance of harmful...
Go to contribution page -
Zhiyuan Pei16/04/2021, 19:17
In this talk, we will present a two-component model of the γ-ray emission which assumes that the total γ-ray output of blazars consists of relativistically beamed and unbeamed components. 584 Fermi/LAT-blazars are listed in our compiled catalogue. This idea leverages the correlation between the radio core-dominance parameter and the γ-ray beaming factor. We firstly propose a so-called "γ-ray...
Go to contribution page -
Giacomo Principe16/04/2021, 19:20
According to radiative models, radio galaxies are predicted to produce gamma rays since the first stages of their evolution. The study of the high-energy emission from young radio sources is crucial for providing information on the most energetic processes associated with these sources, the actual region responsible for this emission, as well as the structure of the newly born radio jets....
Go to contribution page -
Bindu Rani16/04/2021, 19:23
Magnetic reconnection - relinking of magnetic field lines - has been proposed as a possible mechanism to power the high-energy flares in gamma-ray bright Active Galactic Nuclei but has not been confirmed via observations. Our study found observational evidence of magnetic reconnection generated gamma-ray flares in a radio galaxy, 3C 84. In a sequence of radio images, the radio-emitting region...
Go to contribution page -
Rozeena Ebrahim16/04/2021, 19:26
The Circinus galaxy is a composite starburst/Seyfert galaxy which exhibits radio lobes inflated by kpc scale outflows along its minor axis. Its proximity (4 Mpc) makes it a unique target to study the physical nature of these outflows. We investigate if they originate from nuclear star formation activity or if they are jets from an active galactic core. The MeerKAT radio observations allow us...
Go to contribution page -
Monica Orienti17/04/2021, 15:00
Relativistic jets are among the most variable objects in the Universe. Their variability is observed at all energy bands, from radio wavelengths to gamma rays. Despite decades of efforts, many aspects of the physics of relativistic jets remain elusive. In particular, the location and the mechanisms responsible for the high-energy emission and the connection with the variability at different...
Go to contribution page -
Boris Panes, Christopher Eckner, Gabrijela Zaharijas, Gudlaugur Johannesson, Klaas Dijkstra, Luc Hendriks, Roberto Ruiz de Austri, Sascha Caron17/04/2021, 15:00
At GeV energies, the sky is dominated by the interstellar emission from the Galaxy. With limited statistics and spatial resolution, accurate separation of point sources is therefore challenging. In this presentation I will describe the first application of deep learning based algorithms to detect and classify point sources from raw gamma-ray data. To detect point sources we utilise U-shaped...
Go to contribution page -
Rene Breton17/04/2021, 15:00
Spider pulsars refer to the general class of millisecond pulsar binaries comprising a low-mass companion in a tight-enough orbit for the latter to be strongly affected by the energetic pulsar wind. In the radio regime multiple spider systems present extended eclipses which has made them challenging to discover in typical radio surveys. Fermi LAT has considerably changed this picture as...
Go to contribution page -
Natalia Zywucka17/04/2021, 15:15
We present results of Fermi-Large Area Telescope (LAT) light curve (LC) modelling
Go to contribution page
of selected Fermi blazars. All objects possess densely sampled and long-term LCs. For
each blazar we generated three LCs with 7, 10, and 14 days binning, using the latest
4FGL catalogue and binned analysis provided within the fermipy package.
The LCs were modelled with several tools: the Fourier... -
Ivan Kramarenko17/04/2021, 15:15
Within the MOJAVE VLBA program (Monitoring of Jets in AGN with VLBA Experiments) we accumulated observational data at 15 GHz for hundreds of gamma-ray bright active galactic nuclei jets since the beginning of the Fermi observations. We investigated a time delay between flux density of AGN parsec-scale radio emission at 15 GHz and 0.1-100 GeV Fermi LAT photon flux, taken from constructed light...
Go to contribution page -
Dr Zorawar Wadiasingh (NASA GSFC)17/04/2021, 15:15
Black widow (BW) and redback (RB) systems are compact binaries in which the pulsar heats or ablates its low-mass companion by its intense wind of relativistic particles and emission. Radio, optical and X-ray follow-up of unidentified Fermi Large Area Telescope (LAT) sources has expanded the number of these systems from four to nearly 30. Orbital modulation in X-rays suggests that in many...
Go to contribution page -
Albertus Seyffert17/04/2021, 15:30
The wealth of multiwavelength pulsar data has stimulated the development of emission models that predict light curves (LCs) over multiple wavebands, most notably radio and gamma-ray. Using established statistical methods to fit these model LCs to data can prove ineffectual if the data from one waveband are substantially more precise. This waveband—typically radio—dominates the fit and biases...
Go to contribution page -
Raniere de Menezes17/04/2021, 15:30
-
Constantinos Kalapotharakos (UMCP CRESST / NASA GSFC)17/04/2021, 15:30
Modeling of the NICER X-ray waveform of the pulsar PSR J0030+0451 aimed to constrain the neutron star mass and radius has inferred surface hot spots (i.e., the magnetic polar caps) that imply significantly non-dipolar magnetic fields. We investigate magnetic field configurations that comprise offset dipole plus quadrupole components using static vacuum field and force-free global magnetosphere...
Go to contribution page -
Philippe Bruel17/04/2021, 15:45
An important step of a Fermi-LAT data analysis of a Region of Interest consists in performing a binned likelihood fit to find the sky model that, after convolution with the instrument response, best predicts the number of observed counts. The data and model counts are binned in a 3d grid, with two spatial and one spectral dimensions. Checking the goodness-of-fit is not straightforward because...
Go to contribution page -
Hambeleleni Davids17/04/2021, 15:45
Our Galaxy hosts around 160 globular clusters (GCs). The Fermi Large Area Telescope (LAT) has detected about two dozen of them in the GeV band, including Terzan 5. However, only Terzan 5 has plausibly been detected in the very-high-energy range. This unique cluster has also been detected in the radio and X-ray bands. We model the updated broadband spectral energy distribution, attributing this...
Go to contribution page -
Atreya Acharyya17/04/2021, 15:45
We present a study of the gamma-ray emission from the 9 brightest flat spectrum radio quasars (FSRQs) detected with the Fermi Large Area Telescope (LAT) during its first eight years of operation, with the aim of constraining the location of the gamma-ray emission from these objects.
Go to contribution page
Using the brightest flares, we find the shortest variability timescales for our sources, which we then use to... -
Alberto Saldana-Lopez17/04/2021, 16:00
The diffuse extragalactic background light (EBL) is formed by ultraviolet (UV), optical, and infrared (IR) photons mainly produced by star formation processes over the history of the Universe, and contains essential information about galaxy evolution and cosmology. In this talk, we present a new determination of the evolving EBL spectral energy distribution using a novel approach purely based...
Go to contribution page -
Hester Schutte17/04/2021, 16:00
The magnetic field strengths and topologies in blazar jets are not yet well understood. The low-frequency (radio through UV / X-rays) emission from blazars is likely dominated by non-thermal synchrotron emission from relativistic electrons in the jets and is therefore highly polarised, while in the optical through X-ray regime, unpolarised thermal radiation components, e.g., from the accretion...
Go to contribution page -
Alice Harding17/04/2021, 16:00
Ground-based Air-Cherenkov telescopes have detected pulsations at energies above 50 GeV from a growing number of Fermi pulsars. These include the Crab, Vela, PSR B1706-44 and Geminga, with the first two having pulsed detections above 1 TeV. There appears to be VHE emission that is an extension of the Fermi spectra to high energies as well as additional higher-energy components that require a...
Go to contribution page -
Prof. Miguel Mostafa (Penn State University)17/04/2021, 16:15
We will present our follow-up studies of candidate TeV sources. Instead of a blind scan, we searched for significant multi-TeV emission from previously identified targets. Using data from the most recent HAWC sky map (1132 days), we followed up two lists of proposed sources: the sources flagged as good TeV candidates in the Third Catalog of Hard Fermi-LAT Sources (3FHL); and the unassociated...
Go to contribution page -
Lente Dreyer17/04/2021, 16:15
The spectral energy distributions (SEDs) of some blazars exhibit an ultraviolet (UV) and/or soft Xray excess, which can be modelled with different radiation mechanisms. Polarization measurements of the UV/X-ray emission from blazars may provide new and unique information about the astrophysical environment of blazar jets and could thus help to distinguish between different emission scenarios....
Go to contribution page -
Robert Nemiroff17/04/2021, 16:15
Do photons of different energies disperse as they race across the universe? Potential reasons for dispersion include violations of Lorentz invariance, violations of the weak equivalence principle, and electromagnetic interactions with the intervening matter. Which parameters make GRBs the most sensitive to these potential differences: their great distance, being seen over such a wide range of...
Go to contribution page -
Shijie Zheng17/04/2021, 16:30
GECAM (Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor) is an ALL-TIME ALL-SKY monitor for GW EM. It consists of two small satellites in the same Low Earth Orbit (~600 km, 29°) with opposite orbital phase, monitoring instantaneous 100% all-sky from 6 keV to 5 MeV, without a turned-off during the SAA passage.
Go to contribution page
GECAM shall detect several GW GRBs per year jointly with... -
Alyson Joens17/04/2021, 16:45
Joint detections between gravitational waves and gamma-ray bursts (GRBs) enable multi-messenger science and allows for constraints on the neutron star equation of state, tests of fundamental physics, and insight into the origin of the prompt emission. To increase the likelihood of these coincident detections, full sky coverage in the gamma-ray regime is needed. BurstCube aims to expand sky...
Go to contribution page -
Dr Lorenzo Amati (INAF - OAS Bologna)17/04/2021, 17:00
The Transient High-Energy Sky and Early Universe Surveyor (THESEUS) is a space mission concept currently under Phase A study by ESA as candidate M5 mission, aiming at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. Through an unprecedented combination of X-/gamma-rays monitors, an...
Go to contribution page -
Gor Oganesyan17/04/2021, 17:15
The discovery of the joint GRB/GW 170817 events opened a new window into the multi-messenger astronomy. The Advanced gravitational wave detectors of second and third generation will observe larger and larger volume of the Universe. While the current optical surveys will suffer of the faint kilonova emission and many contaminants within the gravitational-wave poor sky-localization, and the ...
Go to contribution page -
Denis Robert Leon Bernard (Centre National de la Recherche Scientifique (FR))17/04/2021, 17:30
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...
Go to contribution page -
Elizabeth Hays (NASA GSFC), Judith Racusin, Markus Boettcher (North-West University), Soebur Razzaque (University of Johannesburg)17/04/2021, 17:45Contributed
-
Pedro De la Torre Luque
Galactic cosmic rays (CR) undergo diffusion by plasma-wave interactions, nuclear reactions with interstellar gas and other processes during their propagation. A good understanding of the diffusion process is crucial for the interpretation of gamma-ray emissions from electron losses (leptonic emissions) as well as hadronic emissions. Current measurements of CR fluxes have reached unprecedented...
Go to contribution page -
Pedro De la Torre Luque
Galactic cosmic rays (CR) undergo diffusion by plasma-wave interactions, nuclear reactions with interstellar gas and other processes during their propagation. A good understanding of the diffusion process is crucial for the interpretation of gamma-ray emissions from electron losses (leptonic emissions) as well as hadronic emissions. Current measurements of CR fluxes have reached unprecedented...
Go to contribution page
Choose timezone
Your profile timezone: