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The Fermi gamma-ray space telescope has revolutionized our view of the gamma-ray sky and the high energy processes in the Universe. While the number of known gamma-ray emitters has increased by orders of magnitude since the launch of Fermi,…

High Energy Astrophysical Phenomena · Physics 2019-05-01 I. Liodakis , D. Blinov

The Gaussian Process Convolution Model (GPCM; Tobar et al., 2015a) is a model for signals with complex spectral structure. A significant limitation of the GPCM is that it assumes a rapidly decaying spectrum: it can only model smooth…

Machine Learning · Statistics 2022-04-15 Wessel P. Bruinsma , Martin Tegnér , Richard E. Turner

The Fermi Gamma-ray Observatory discovered about a thousand extragalactic sources emitting energy from 100 MeV to 100 GeV. The majority of these sources belong to the class of blazars characterized by a quasi-featureless optical spectrum…

Astrophysics of Galaxies · Physics 2017-11-02 Simona Paiano , Renato Falomo , Marco Landoni , Aldo Treves , Riccardo Scarpa

In this paper we present the Fermi All-sky Variability Analysis (FAVA), a tool to systematically study the variability of the gamma-ray sky measured by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. For each…

High Energy Astrophysical Phenomena · Physics 2013-07-15 LAT Collaboration

A majority of the $\gamma$-ray emission from star-forming galaxies is generated by the interaction of high-energy cosmic rays with the interstellar gas and radiation fields. Star-forming galaxies are expected to contribute to both the…

Astrophysics of Galaxies · Physics 2020-05-20 M. Ajello , M. Di Mauro , V. S. Paliya , S. Garrappa

Structure formation in our Universe creates non-Gaussian random fields that will soon be observed over almost the entire sky by the Euclid satellite, the Vera-Rubin observatory, and the Square Kilometre Array. An unsolved problem is how to…

Cosmology and Nongalactic Astrophysics · Physics 2021-12-10 Joey R. Braspenning , Elena Sellentin

We study a family of parametric statistical models based on gamma distributions, which do give realistic descriptions for other stochastic porous media. Gamma distributions contain as a special case the exponential distributions, which…

Astrophysics · Physics 2016-08-30 C. T. J. Dodson

A significant point-like component from the small scale (or discrete) structure in the H2 interstellar gas might be present in the Fermi-LAT data, but modeling this emission relies on observations of rare gas tracers only available in…

High Energy Astrophysical Phenomena · Physics 2023-03-29 Alexander Shmakov , Mohammadamin Tavakoli , Pierre Baldi , Christopher M. Karwin , Alex Broughton , Simona Murgia

The Fermi Large Area Telescope has provided the most detailed view toward the Galactic Centre (GC) in high-energy gamma rays. Besides the interstellar emission and point-source contributions, the data suggest a residual diffuse gamma-ray…

Astrophysics of Galaxies · Physics 2018-02-07 Giacomo Fragione , Fabio Antonini , Oleg Y. Gnedin

Very-high-energy (VHE, E \gtrsim 100 GeV) gamma rays emitted by extragalactic sources, such as blazars, initiate electromagnetic cascades in the intergalactic medium. The cascade photons arrive at the earth with angular and temporal…

High Energy Astrophysical Phenomena · Physics 2011-06-17 H. Huan , T. Weisgarber , T. Arlen , S. P. Wakely

The source-count distribution as a function of their flux, dN/dS, is one of the main quantities characterizing gamma-ray source populations. We employ statistical properties of the Fermi Large Area Telescope (LAT) photon counts map to…

High Energy Astrophysical Phenomena · Physics 2016-07-28 Hannes-S. Zechlin , Alessandro Cuoco , Fiorenza Donato , Nicolao Fornengo , Andrea Vittino

Interactions of grazing incidence, ultra high energy cosmic rays with the earth's atmosphere may provide a new method of studying energetic cosmic rays with gamma-ray satellites. It is found that these cosmic ray interactions may produce…

Astrophysics · Physics 2010-11-01 Andrew Ulmer

Here is reviewed our current understanding of Galactic and extragalactic diffuse gamma-ray emission. The spectrum of the extragalactic gamma-ray background above 30 MeV can be well described by a power law with photon index s=2.1. In the…

Astrophysics · Physics 2007-05-23 Martin Pohl

Gamma rays from extragalactic sources are attenuated by pair-production interactions with diffuse photons of the extragalactic background light (EBL). Gamma-ray bursts (GRBs) are a source of high-redshift photons above 10 GeV, and could be…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-14 Rudy C. Gilmore , Francisco Prada , Joel R. Primack

The all-sky survey in high-energy gamma rays (E$>$30 MeV) carried out by the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma-Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray…

Astrophysics · Physics 2011-05-05 P. Sreekumar

Predefined spatial templates to describe the background of $\gamma$-ray emission from astrophysical processes, like cosmic ray interactions, are used in previous searches for the $\gamma$-ray signatures of annihilating galactic dark matter.…

High Energy Astrophysical Phenomena · Physics 2016-06-22 Xiaoyuan Huang , Torsten Enßlin , Marco Selig

We analyze the first two years of data from the Fermi Gamma Ray Space Telescope from the direction of the inner 10 degrees around the Galactic Center with the intention of constraining, or finding evidence of, annihilating dark matter. We…

High Energy Physics - Phenomenology · Physics 2015-03-17 Dan Hooper , Lisa Goodenough

Data from the Fermi Large Area Telescope suggests that there is an extended excess of GeV gamma-ray photons in the Inner Galaxy. Identifying potential astrophysical sources that contribute to this excess is an important step in verifying…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-03 Samuel K. Lee , Mariangela Lisanti , Benjamin R. Safdi

Previous searches for the $\gamma$-ray signatures of annihilating galactic dark matter used predefined spatial templates to describe the background of $\gamma$-ray emission from astrophysical processes like cosmic ray interactions. In this…

High Energy Astrophysical Phenomena · Physics 2016-04-25 Xiaoyuan Huang , Torsten Enßlin , Marco Selig