Conveners
Gamma-Ray Astrophysics: Instrument + ExGal I
- Elina Lindfors (U)
Gamma-Ray Astrophysics: Instrument + ExGal I
- Daniel Mazin (IFAE)
Gamma-Ray Astrophysics: Instrument + exGal II
- Marianne Lemoine-Goumard (CNRS)
Gamma-Ray Astrophysics: Gamma-Ray Physics
- Luigi Tibaldo (SLAC)
Gamma-Ray Astrophysics: Galactic
- Valerie Connaughton
Gamma-Ray Astrophysics: Special Session - Gamma Rays from the Galactic Centre
- Christoph Weniger (University of Amsterdam)
Gamma-Ray Astrophysics: Galactic (rescheduled)
- There are no conveners in this block
Gamma-Ray Astrophysics: Galactic
- Nepomuk Otte
Dirk Lennarz
(Georgia Tech)
6/23/14, 2:30 PM
Gamma-Ray Astrophysics
Presentation
The High Altitude Water Cherenkov (HAWC) observatory is an extensive air shower (EAS) detector currently under construction in central Mexico at an altitude of 4,100 m above sea level. It improves the water Cherenkov technique, where gamma rays in the 100 GeV - 100 TeV range are detected by measuring Cherenkov light from secondary particles, by having an order of magnitude better sensitivity,...
Prof.
Christian Stegmann
(DESY)
6/23/14, 2:50 PM
Gamma-Ray Astrophysics
Presentation
The H.E.S.S. telescope system is operating since more than 10 years and the collaboration contributes significantly to the rapidly progressing field of ground-based gamma-ray astronomy. With the recent start of the operation of a new telescope with a mirror diameter of 28m the detection capabilities if the H.E.S.S. telescope system are significantly enhanced and the energy threshold is much...
Melissa Pesce-Rollins
(INFN-Pisa)
6/23/14, 3:10 PM
Gamma-Ray Astrophysics
Presentation
During its first six years of operation, the Fermi Large Area Telescope (LAT) has detected >30 MeV gamma-ray emission from more than 40 solar flares, nearly a factor of 10 more than EGRET detected. Detections sample both the impulsive phase and long-duration emission, extending up to ~20 hours for the 2012 March 7 X-class flares, and include the first detection of >100 MeV emission from a...
Daniela Hadasch
(University of Innsbruck)
6/23/14, 3:30 PM
Gamma-Ray Astrophysics
Presentation
The small source class of gamma-ray binaries consists at present of six known objects with different orbital periods ranging from days up to several years. One of the best studied gamma-ray binary across all frequencies, LS I +61 303, is highly variable at any given orbital phase and was lately discovered to show on top of orbital also superorbital variability at high energies. In contrary,...
Keith Bechtol
6/23/14, 4:30 PM
Gamma-Ray Astrophysics
Presentation
Galaxy clusters are unique environments to study cosmic-ray acceleration. In comparison to Galactic accelerators, large-scale structure formation shocks associated with merger events and accretion have lower Mach numbers and occur in high-temperature weakly magnetized plasma. Leptonic cosmic rays in clusters are well established observationally through studies of Mpc-scale diffuse radio halos...
Fabio Zandanel
(University of Amsterdam)
6/23/14, 4:50 PM
Gamma-Ray Astrophysics
Presentation
Relativistic particles are revealed in clusters of galaxies from observations of diffuse synchrotron radio emission. At least part of this emission can be originated by secondary electrons produced by cosmic-ray protons interacting with the protons of the intra-cluster medium. This should be accompanied by the production of gamma rays, potentially detectable by the Fermi satellite and...
Ralph Bird
(UCD Dublin)
6/23/14, 5:05 PM
Gamma-Ray Astrophysics
Presentation
VERITAS, an array of 12 m imaging atmospheric Cherenkov telescopes in southern Arizona, is one of the world's most sensitive detectors of astrophysical very-high-energy (VHE, > 100 GeV) gamma rays. The current status of the VERITAS observations of M 31 (Andromeda Galaxy) including an upper limit on the VHE flux, an updated analysis of the Fermi-LAT data and a comparison with theoretical...
Dr
Valerie Connaughton
(National Space Science and Technology Centre)
6/23/14, 5:20 PM
Gamma-Ray Astrophysics
Presentation
Our understanding of high-energy emission from Gamma-Ray Bursts has greatly advanced with observations from the Fermi gamma-ray space telescope. I will review the Fermi observations and explain why they give hope to the very high-energy communities in their quest for Gamma-Ray Burst detections with the High Altitude Water Cherenkov (HAWC) and Cherenkov Telescope Array (CTA) experiments. I...
Dirk Lennarz
(Georgia Tech)
6/23/14, 5:40 PM
Gamma-Ray Astrophysics
Presentation
The temporal evolution and end of GRB spectra have important implications for the acceleration mechanisms of gamma-ray bursts (GRBs). Above $\approx10$ GeV the effective area of \emph{Fermi}-LAT is approximately constant and since the photon flux is steeply decreasing with energy, an insufficient number of photons is detected. The High Altitude Water Cherenkov (HAWC) observatory is a gamma-ray...
Maxim Piskunov
(Institute for Nuclear Research RAS)
6/23/14, 5:55 PM
Gamma-Ray Astrophysics
Presentation
Numerous observations confirm that the high energy (> 100 MeV) emission of gamma ray bursts is delayed with respect to the low energy emission. However, the difference of light curves in various high energy bands has not been studied properly.
In this paper we consider all the bursts observed by Fermi-LAT since 2008 August 4 to 2011 August 1, for which at least 10 events with energies 1 GeV...
Dr
Robert Parsons
(Max-Planck-Institut für Kernphysik)
6/23/14, 6:10 PM
Gamma-Ray Astrophysics
Presentation
We present a high-performance event reconstruction algorithm: an Image Pixel-wise fit for Atmospheric Cherenkov Telescopes (ImPACT). This gamma-ray event reconstruction algorithm is based around the comparison of camera pixel amplitudes to an expected image template, performing a maximum likelihood fit to find the best-fit shower parameters. Related reconstruction algorithms have already been...
Sheldon Campbell
(T)
6/23/14, 6:25 PM
Gamma-Ray Astrophysics
Presentation
Spatial fluctuations of astrophysical signals are a powerful probe of source distributions, radiation production mechanisms, and propagation effects. The precision of measuring angular power spectra is currently estimated as a combination of shot noise, instrument systematics, and cosmic variance. We show that an important contribution, dependent on the finite statistics of the experiment, has...
Dr
Nepomuk Otte
(Georgia Institute of Technology)
6/24/14, 2:30 PM
Gamma-Ray Astrophysics
Presentation
VERITAS is an array of four 12 m class Cherenkov telescopes for very-high-energy gamma-ray (>50 GeV) observations. The VERITAS Collaboration completed a series of upgrades in summer 2012 with the objective of lowering the energy threshold and improving the sensitivity of the array at all accessible energies. One telescope was relocated, the trigger system was replaced, and the cameras were...
Dr
Emiliano Carmona
(CIEMAT)
6/24/14, 2:50 PM
Gamma-Ray Astrophysics
Presentation
MAGIC, the system of two imaging atmospheric Cherenkov telescopes located at the Canary island of La Palma, has successfully explored the very-high-energy (VHE) sky in stereoscopic mode since 2009. Thanks to its two 17-m diameter mirror dishes, MAGIC has provided unique results in the low-energy range of ground-base gamma-ray astronomy. In addition, the substantial upgrades introduced in the...
Andrii Neronov
(Universite de Geneve (CH))
6/24/14, 3:10 PM
Gamma-Ray Astrophysics
Presentation
I will review the techniques of the measurement of optical / infrared extragalactic background light (EBL) and of intergalactic magnetic fields (IGMF) using the effect of absorption of very-high-energy gamma-rays in the intergalactic medium. I will summarise the existing constraints on both EBL and IGMF and discuss perspectives of improvement of the measurements with the next generation...
Elina Lindfors
(U)
6/24/14, 3:30 PM
Gamma-Ray Astrophysics
Presentation
The detection of Flat Spectrum Radio Quasars (FSRQs) in the Very High Energy (VHE, E>100 GeV) range is challenging, mainly because of their steep soft spectra and relatively large distances. Nevertheless three FSRQs are now known to be VHE emitters, all of them have been detected by the MAGIC telescopes. The detection of the VHE gamma-rays has challenged the emission models of these sources....
Markus Ackermann
(D)
6/24/14, 4:30 PM
Gamma-Ray Astrophysics
Presentation
The data collected by the Fermi Large Area Telescope (LAT) enable a huge step forward in measuring and understanding the origins of the isotropic gamma-ray background (IGRB) . The IGRB originates from the superposition of different populations of unresolved sources with possible contributions from genuinely diffuse and exotic processes. In most parts of the sky it is sub-dominant to the...
Amy Furniss
6/24/14, 4:50 PM
Gamma-Ray Astrophysics
Presentation
Gamma-ray blazars are among the most extreme astrophysical sources, harboring phenomena far more energetic than those attainable by terrestrial accelerators. These galaxies are understood to be active galactic nuclei that are powered by accretion onto supermassive black holes and have relativistic jets pointed along the Earth line of sight. The emission displayed is variable at all...
278.
Extended Blazar Observations by VERITAS and Implications for the Extragalactic Background Light
Mr
Yerbol Khassen
(University College Dublin)
6/24/14, 5:10 PM
Gamma-Ray Astrophysics
Presentation
The VERITAS Collaboration has been conducting long-term observations of several TeV blazars at a variety of redshifts to characterise their temporal and spectral properties. The very high energy (VHE, >100 GeV) spectra of TeV blazars are expected to show energy-dependent absorption that increases with redshift due to the interaction of VHE photons with infra-red photons of the extragalactic...
Prof.
Karl Mannheim
(University Wuerzburg)
6/24/14, 5:25 PM
Gamma-Ray Astrophysics
Presentation
Radio galaxies are a prime target for studies of the processes that lead to the formation of extragalactic jets. Their spectral energy distributions do not agree with the ones of blazars after an appropriate increase of the orientation angle. In fact, the de-boosted emission from the relativistic jets opens the view to the magnetospheric jet formation region associated with accreting...
Dr
Giovanni Piano
(INAF)
6/24/14, 5:45 PM
Gamma-Ray Astrophysics
Presentation
The AGILE space mission, currently in its eight year of operations in orbit, obtained a large number of crucial and unexpected results. We will review the main results for both Galactic and extragalactic sources, and outline some of the most surprising discoveries (gamma-ray flares from the Crab Nebula, detection of Cygnus X-3 and Cygnus X-1 in coincidence with special spectral transitions,...
Dr
M. Angeles Perez-Garcia
(University of Salamanca and IUFFyM)
6/24/14, 6:05 PM
Gamma-Ray Astrophysics
Presentation
We propose that the existing population of neutron stars in the galaxy can help constrain the nature of decaying dark matter. The amount of decaying dark matter, accumulated in the central regions in neutron stars and the energy deposition rate from decays, may set a limit on the neutron star survival rate against transitions to more compact stars and, correspondingly, on the dark matter...
foteini oikonomou
(University College London)
6/24/14, 6:20 PM
Gamma-Ray Astrophysics
Presentation
High frequency peaked, high redshift blazars, are extreme in the sense that their spectrum is particularly hard and peaks at TeV energies. Standard leptonic scenarios often require peculiar source parameters and/or a special setup in order to account for these observations. Electromagnetic cascades seeded by ultra-high energy cosmic rays (UHECRs) in the intergalactic medium have also been...
Ms
Emma De Ona Wilhelmi
(IEEC-CSIC Barcelona)
6/25/14, 2:00 PM
Gamma-Ray Astrophysics
Presentation
The last few years have witness a revolution in very high
gamma-ray astronomy (VHE; E>100 GeV) driven largely by a new generation of
Cherenkov telescopes. These new facilities,
namely H.E.S.S. and the new 28-meter-sized mirror H.E.S.S. 2, MAGIC and
its upgrade MAGIC 2 and Veritas were designed to increase the
flux sensitivity in the energy regime of hundreds of GeV, expanding...
Dr
Marie-Helene GRONDIN
(CENBG, Bordeaux, France)
6/25/14, 2:20 PM
Gamma-Ray Astrophysics
Presentation
Successfully launched on June 11, 2008, the Large Area Telescope (LAT), aboard the Fermi Gamma-ray Space Telescope is sensitive to gamma-rays with energies from about 20 MeV to more than 300 GeV and covers the full sky every 3 hours. The improved sensitivity and the unprecedented statistics offered by the LAT in comparison to its predecessor EGRET enable the study of various classes of...
Stefan Ohm
(D)
6/25/14, 2:35 PM
Gamma-Ray Astrophysics
Presentation
HESS J1640$-$465 is among the brightest Galactic TeV gamma-ray sources ever discovered by the High Energy Stereoscopic System (H.E.S.S.). Its likely association with the shell-type supernova remnant (SNR) G338.3$-$0.0 at a distance of $\sim$10 kpc makes it the most luminous Galactic source in the TeV regime.
Our recent analysis of follow-up observations with H.E.S.S. reveal a significantly...
Lucas Guillemot
(L)
6/25/14, 2:50 PM
Gamma-Ray Astrophysics
Presentation
Observations of the gamma-ray sky with the Large Area Telescope (LAT) on the Fermi satellite have revealed significant pulsations from about 150 young and recycled, millisecond pulsars. These observations have shown that pulsars are by far the largest source class in the Galactic plane at GeV energies, and new pulsars are still continuously being found at the locations of LAT sources with no...
Regis Terrier
(C)
6/25/14, 3:10 PM
Gamma-Ray Astrophysics
Presentation
The centre of our Galaxy is a major laboratory for high energy astrophysics. In particular, it harbours the closest supermassive black hole (SMBH) to us. Its luminosity is extremely low for an object of several million solar masses but there is growing evidence that it
experienced periods of much stronger activity in the past. A sustained star formation activity is also taking place in the...
Luigi Tibaldo
(SLAC)
6/25/14, 3:30 PM
Gamma-Ray Astrophysics
Presentation
The Milky Way shines in gamma rays from MeV to above TeV energies due to interactions of high-energy cosmic rays with interstellar gas and radiation fields. I will review the current status and future challenges for both space-borne and ground-based observations, and I will discuss some implications for the physics of cosmic rays and of the interstellar medium, as well as for the modeling of...
Wim De Boer
(KIT - Karlsruhe Institute of Technology (DE))
6/26/14, 1:45 PM
Gamma-Ray Astrophysics
Presentation
A survey of the diffuse gamma-ray sky revealed 'bubbles' of emission above and below the Galactic disc symmetric around the centre of the Milky Way, so they are presumed to be from the centre with a height of 10 kpc. They have been proposed to be blown by cosmic rays originating from the star formation in the Galactic Centre, or jet activity from the supermassive black hole in the GC, or even...
Tim Linden
(U)
6/26/14, 2:00 PM
Gamma-Ray Astrophysics
Presentation
Gamma-Ray observations by the Fermi-LAT have uncovered a substantial population of gamma-ray bright pulsars in our galaxy. Using 5.5 years of Fermi data, we measure the spectrum and morphology of both the young and recycled pulsars, and show current data allows for a direct measurement of the gamma-ray luminosity function of the pulsar population. We apply the results of our analysis to the...
Nicholas Rodd
(M)
6/26/14, 2:15 PM
Gamma-Ray Astrophysics
Presentation
Recent work has confirmed the presence of a gamma-ray excess in data from the Fermi Space Telescope extending at least 10 degrees from the Galactic Center. I will describe recent progress in characterizing this signal by using photons with the highest quality angular reconstruction, with an emphasis on the extended "inner galaxy" region. I will focus on cross-checks we have performed to...
Stephen Portillo
(Harvard University)
6/26/14, 2:25 PM
Gamma-Ray Astrophysics
Presentation
The Large Area Telescope on the Fermi Gamma-ray Space Telescope has a point spread function with large tails, consisting of events affected by tracker inefficiencies, inactive volumes, and hard scattering; these tails can make source confusion a limiting factor. The parameter CTBCORE, available in the publicly available Extended Fermi-LAT data, estimates the quality of each event's direction...
Tansu Daylan
(H)
6/26/14, 2:40 PM
Gamma-Ray Astrophysics
Presentation
The recently discovered gamma-ray excess in the inner galaxy has important implications either for astrophysics or dark matter. Regardless of its origin, studies on the anomalous emission suffer from poor astrophysical modeling and large uncertainties in background emission in the region of interest. Therefore understanding of the gamma-ray background components in the inner galaxy is...
Francesca Calore
(University of Amsterdam)
6/26/14, 2:55 PM
Gamma-Ray Astrophysics
Recently, a spatially extended excess of gamma rays compatible with a DM signal from the inner region of the Milky Way has been claimed by different and independent groups, using Fermi LAT data. Yet, final statements about the morphology and spectral properties of such an extended diffuse emission are under debate, given the high complexity of this sky region. In this talk I will present an...
Mr
Thomas Lacroix
(Institut d'Astrophysique de Paris (IAP))
6/26/14, 3:05 PM
Gamma-Ray Astrophysics
Presentation
An excess of gamma rays at GeV energies has been detected in the Fermi-LAT data. This signal comes from a narrow region around the Galactic Center and has been interpreted as possible evidence for light (10-30 GeV) dark matter particles annihilating either into a mixture of leptons-antileptons and $b\bar{b}$ or into $b\bar{b}$ only. Focussing on the prompt gamma-ray emission, previous work...
Martin Vollmann
6/26/14, 3:15 PM
Gamma-Ray Astrophysics
In this brief presentation, I will discuss how cosmic-ray and radio observations impose stringent constraints on dark matter (DM) candidates with masses in the ~1-50 GeV range. We find strong bounds on DM annihilating into light leptons, or democratically into all leptons from cosmic ray positron data, while complementarily, cosmic ray antiproton and radio data show considerable tension with...
Dr
Alex Geringer-Sameth
6/26/14, 3:25 PM
Gamma-Ray Astrophysics
I will present the latest results from a search for dark matter annihilation in a large sample of Milky Way dwarf galaxies. Nearly 6 years of data from the Fermi Gamma-ray Space Telescope are analyzed by weighting individual photons based on their spatial and spectral properties. Such searches are powerful enough to probe the relic abundance cross section for some dark matter masses. I will...
Lars Bergstrom
(Stockholm University)
6/26/14, 3:35 PM
Gamma-Ray Astrophysics
Daniela Hadasch
(University of Innsbruck)
6/27/14, 2:30 PM
Gamma-Ray Astrophysics
Presentation
MAGIC is a system of two atmospheric Cherenkov telescopes located in the Canary island of La Palma.
MAGIC has low energy threshold, down to 50 Gev, well suited to study the still poorly explored energy band below 100 GeV. Although the space-borne gamma-ray telescope Fermi/LAT is sensitive up to 300 GeV, gamma-ray rates drop fast with increasing energy, and statistics are scarce above few...
Aion Viana
(M)
6/27/14, 2:45 PM
Gamma-Ray Astrophysics
Presentation
The Galactic Centre region has been observed by the complete H.E.S.S.-I array of ground-based Cherenkov telescopes since 2004 leading to the detection of the very-high-energy (VHE, E > 100 GeV)gamma-ray source HESS J1745-290 coincident in position with the supermassive black hole Sgr A*.
A TeV gamma-ray diffuse emission has been detected along the Galactic ridge, very likely to be related to...
Anna Franckowiak
(SLAC/KIPAC)
6/27/14, 3:00 PM
Gamma-Ray Astrophysics
Presentation
The Fermi bubbles are two large structures in the gamma-ray sky extending up to 55 deg above and below the Galactic center. We present our analysis of 50 months of Fermi-LAT pass7 reprocessed data from 100 MeV to 500 GeV above 10 deg in Galactic latitude to derive the spectrum and morphology of the Fermi bubbles. We perform a detailed study of the systematic uncertainties due to the modeling...
Douglas Finkbeiner
(Harvard University)
6/27/14, 3:20 PM
Gamma-Ray Astrophysics
Presentation
The strongest WIMP annihilation signals are expected from the inner
Milky Way, but foreground contribution from cosmic-ray interactions
with the gas and radiation field are strongest there as well.
Therefore, indirect detection has been hampered by insufficient
knowledge of the diffuse gamma-ray foregrounds. Improved modeling
requires a 3D map of gas and dust (for $\pi^0$ and brem...
Dr
Meng Su
(MIT, USA)
6/27/14, 3:35 PM
Gamma-Ray Astrophysics
Presentation
We propose a high angular resolution telescope dedicated to the sub-GeV
gamma-ray astronomy as a candidate for the CAS-ESA joint small mission.
This mission, called PANGU (PAir-productioN Gamma-ray Unit), will open up a
unique window of electromagnetic spectrum that has never been explored with
great precision. A wide range of topics of both astronomy and fundamental
physics can be...
