Conveners
Gamma-ray astrophysics: I
- David Paneque (Max Planck Institute for Physics, Munich)
Gamma-ray astrophysics: II
- Francesca Calore (University of Amsterdam)
Gamma-ray astrophysics: III
- Francesca Calore (University of Amsterdam)
Gamma-ray astrophysics: IV
- David Paneque (Max Planck Institute for Physics, Munich)
The field of gamma-ray astronomy has experienced impressive progress over the last decade. Thanks to the advent of a new generation of imaging air Cherenkov telescopes (H.E.S.S., MAGIC, VERITAS) and thanks to the launch of the Fermi-LAT satellite, several thousand gamma-ray sources are known today, revealing an unexpected ubiquity of particle acceleration processes in the Universe. Major...
The Compton Spectrometer and Imager (COSI) is a balloon-borne, gamma ray imager, spectrometer, and polarimeter with sensitivity from 0.2 to 5 MeV. Utilizing a compact Compton telescope design with twelve cross-strip, high-purity germanium detectors, COSI has three main science goals: study the 511 keV positron annihilation line from the galactic plane, image diffuse emission from stellar...
I will first describe the experimental setup with which we took data at different photon energies from 1.7MeV to 74MeV, and with different polarisation configurations.
I will present the software I developed to reconstruct the photon conversion events, especially for low energies.
I will also introduce the complete detailed simulation I made of the detector.
Finally I will present the...
The CALET Gamma-ray Burst Monitor (CGBM) is the secondary scientific instrument of the CALET mission on the International Space Station (ISS), which was successfully launched and attached to the International Space Station (ISS) at the end of August 2015 and began scientific operations in October 2015.
The CGBM consists of two LaBr3(Ce) and one BGO scintillators, each read by a single...
The High Altitude Water Cherenkov (HAWC) Observatory has been fully operational since its inauguration on 20 March 2015. HAWC opens a new window for survey observations of gamma rays and cosmic rays in the very high energy (VHE) range from 100 GeV to 100 TeV, facilitating studies of Galactic and extragalactic particle accelerators, indirect dark matter searches, gamma-ray bursts, and many...
We present the new Third Catalog of Hard Fermi-LAT Sources, dubbed 3FHL, which describes the sky at energies above 10 GeV. Relying on 7 years of data and the Pass 8 event level analysis, this catalog reports the detection of more than 1700 sources, representing a huge step forward relative to the 1FHL, which characterizes the sky at the same energies. The improved flux sensitivity (factor of...
A broadband study of high-z (z>3) blazars enables us to understand the evolution of the properties of relativistic jets over cosmic time. Moreover, it has been found in many studies that such high-z blazars host extremely massive black holes (M$_{BH}$> 1e9 M$_{\odot}$) and thus shed a new light on the formation of supermassive black holes in the early Universe. Here we report the first...
The blazars Mrk421 and Mrk501 are among the brightest keV and TeV sources in the sky, and among the few sources whose (radio to VHE gamma-rays) Spectral Energy Distributions (SEDs) can be characterized by current instruments by means of relatively short observations (minutes to hours). Consequently, Mrk421 and Mrk501 can be studied with a larger degree of accuracy than most of the other...
The main results from our analysis are :
(1) nature of processes generating
flux variability at optical/radio frequencies is different from
those at GeV freqeuncies ($\beta \sim $ 2 and 1, respectively); this could
imply, that $\gamma-$ray variability, unlike the Synchrotron (radio-to-optical) one,
is generated by superposition of two stochastic processes with different
relaxation...
PKS1510-089 is a flat spectrum radio quasar with a redshift of 0.36 and is one of the few such sources detected in very-high-energy (VHE, >100 GeV) gamma rays. PKS1510-089 is highly variable at GeV energies, but until recently no variability in the VHE range has been observed.
In 2015 May PKS1510-089 showed a high state in optical and in the GeV range. MAGIC observations performed at that...
Massive black holes in active galaxies are surrounded by bulges of both evolved late type and also young luminous stars in nuclear stellar clusters. The luminous stars can enter a jet region which contain fast moving blobs filled with relativistic electrons. We calculate
the gamma-ray spectra and light curves produced by these electrons in the Inverse Compton electron-positron pair cascade...
Angular power spectrum is getting more and more important in recent years to study components of the diffuse gamma-ray background. Understanding constituents through this and other measurements is extremely important for our generic knowledge on high-energy sky. If we are interested in searching for new physics such as dark matter annihilation, it is essential to address all possible...
will be based on
A.~Cuoco, J.~Q.~Xia, M.~Regis, E.~Branchini, N.~Fornengo and M.~Viel,
%``Dark Matter Searches in the Gamma-ray Extragalactic Background via Cross-correlations With Galaxy Catalogs,''
Astrophys.\ J.\ Suppl.\ {\bf 221} (2015) no.2, 29
doi:10.1088/0067-0049/221/2/29
[arXiv:1506.01030 [astro-ph.HE]]
M.~Regis, J.~Q.~Xia, A.~Cuoco, E.~Branchini, N.~Fornengo...
Review talk on the high-energy interstellar gamma-ray emission from the Milky Way
Despite several gamma-ray observational campaigns of clusters of galaxies in the last years, both by Fermi-LAT and Cherenkov telescopes, the diffuse high-energy emission that is expected to come from cosmic-ray hadronic interactions with the abundant ambient gas remains elusive. Nevertheless, we significantly improved our understanding of non-thermal phenomena in clusters. I will summarize the...
Statistical properties of photon count maps have recently been proven to provide a sensitive observable for characterizing gamma-ray source populations and for measuring the composition of the gamma-ray sky with high accuracy. In this contribution, we generalize the use of the standard 1-point probability distribution function (1pPDF) to decompose the high-latitude gamma-ray emission observed...
In this talk, I will present an analysis of the extragalactic gamma-ray background (EGB) using data from the Fermi Large Area Telescope. The method takes advantage of photon-count statistics to determine the properties of resolved and unresolved gamma-ray sources that contribute to the EGB. I will present the source-count functions, as a function of energy, from 1.89 GeV to 2 TeV, as well as...
We present a comprehensive search for angular extension in high-latitude gamma-ray sources detected by the Fermi Large Area Telescope (LAT). While the majority of high-latitude LAT sources are extragalactic blazars that appear point-like within the LAT angular resolution, there are several physics scenarios that predict the existence of populations of spatially extended sources. Gamma-ray...
We consider particle acceleration in the vacuum gaps in split-monopole magnetospheres of slow and maximally rotating black holes, embedded in the radiatively-inefficient accretion flow (RIAF) environment. The gap height is limited by the onset of gamma-gamma pair production on the infrared photons originating in the RIAF.
We numerically calculate the acceleration and propagation of charged ...
Most of the 200 gamma-ray pulsars detected by the Fermi-LAT space telescope exhibit sharp spectral cutoffs around a few GeV. This can be explained by classical pulsar models, in which gamma-ray emission originates from curvature radiation emitted by e-/+ pairs, accelerated either close to the neutron star surface or to the pulsar light cylinder. These models naturally predict the observed...
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Low-latitude Fermi-LAT data, together with the high resolution gas (CO & HI) and the dust opacity maps, has been recently exploited to study the radial emissivity of γ-rays induced by interactions of cosmic rays (CRs) with the interstellar medium along the Galactic Plane.
Both the absolute emissivity and the energy spectra of γ-rays exhibit significant variations along the galactic...
A.Donath on behalf of the H.E.S.S. collaboration.
H.E.S.S. (High Energy Stereoscopic System) is a hybrid array of five imaging
atmospheric Cherenkov telescopes in Namibia, operating in the very-high-energy (VHE) gamma-ray energy range between ~20 GeV and 100 TeV. In the past decade H.E.S.S. has conducted deep observations of Galactic regions of utmost importance for understanding...
There are several types of Galactic sources that can potentially accelerate charged particles up to GeV and TeV energies. These accelerated particles can produce Very High Energy (VHE) gamma-ray emission through different processes like inverse Compton scattering of ambient photon fields by accelerated electrons.
We present here the results of our observations on X-ray and gamma-ray binaries...
Gamma Cygni SNR (G78.2+2.1) is one of the first supernova remnants (SNR) detected in the high-energy gamma-ray band. It is a middle-aged SNR (~7000 years old) situated in the Cygnus region. The high-energy observations by VERITAS and Fermi-LAT revealed a complex, energy-dependent morphology of the SNR in the GeV-TeV band, different from that observed in X-rays. G78.2+2.1 also hosts the pulsar...
Models of the extragalactic gamma-ray background (EGB) show that its intensity can be ascribed to the integrated emission of source populations already detected by the Fermi Large Area Telescope (LAT). Taking advantage of the sensitivity increase yielded by Pass 8, the new event-level analysis, we tested this hypothesis employing a photon fluctuation analysis above 50 GeV. For the first time...
