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The Cygnus Loop is a nearby supernova remnant (SNR) observed across the electromagnetic spectrum. With the analysis of 6 years of Fermi/LAT data we find that, what previous studies had considered a single source, consists of an extended…

High Energy Astrophysical Phenomena · Physics 2015-03-04 I. Reichardt , R. Terrier , J. West , S. Safi-Harb , E. de Oña-Wilhelmi , J. Rico

Excess of gamma rays around the Galactic center (GC) observed in the Fermi Large Area Telescope (LAT) data is one of the most intriguing features in the gamma-ray sky. The spherical morphology and the spectral energy distribution with a…

High Energy Astrophysical Phenomena · Physics 2025-03-13 Dmitry V. Malyshev

More than 90% of the Galactic gas-related gamma-ray emissivity above 1 GeV is attributed to the decay of neutral pions formed in collisions between cosmic rays and interstellar matter, with lepton-induced processes becoming increasingly…

High Energy Astrophysical Phenomena · Physics 2019-08-13 C. D. Dermer , A. W. Strong , E. Orlando , L. Tibaldo

We present a solution to the apparent discrepancy between the radial gradient in the diffuse Galactic gamma-ray emissivity and the distribution of supernova remnants, believed to be the sources of cosmic rays. Recent determinations of the…

Astrophysics · Physics 2009-11-10 A. W. Strong , I. V. Moskalenko , O. Reimer , S. Digel , R. Diehl

In this work, we revisit the all-sky Galactic diffuse $\gamma$-ray emission taking into account the new measurements of cosmic ray electron/positron spectrum by PAMELA, ATIC and Fermi, which show excesses of cosmic electrons/positrons…

High Energy Astrophysical Phenomena · Physics 2014-11-20 Juan Zhang , Qiang Yuan , Xiao-Jun Bi

Several cosmic ray experiments have measured excesses in electrons and positrons, relative to standard backgrounds, for energies from ~ 10 GeV - 1 TeV. These excesses could be due to new astrophysical sources, but an explanation in which…

High Energy Astrophysical Phenomena · Physics 2014-11-20 Spencer Chang , Lisa Goodenough

The origin of the Fermi bubbles, which constitute two gamma-ray emitting lobes above and below the Galactic plane, remains unclear. The possibility that this Fermi bubbles gamma-ray emission originates from hadronic cosmic rays advected by…

High Energy Astrophysical Phenomena · Physics 2022-12-07 Olivier Tourmente , Donna Rodgers-Lee , Andrew M. Taylor

Gamma-ray emission from large structures is useful for tracing the propagation and distribution of cosmic rays throughout our Galaxy. For example, the search for gamma-ray emission from Giant Molecular Clouds may allow us to probe the flux…

High Energy Astrophysical Phenomena · Physics 2019-08-13 Henrike Fleischhack , Hugo Alberto Ayala Solares , Petra Huentemeyer , Matthew Coel

Under nonuniform convection, the distribution of diffusive particles can exhibit dipole and quadrupole anisotropy induced by the fluid inertial and shear force, respectively. These convection-related anisotropies, unlike the Compton-Getting…

High Energy Astrophysical Phenomena · Physics 2022-10-26 Yiran Zhang , Siming Liu , Dejin Wu

In this paper, we compile a \emph{Fermi} sample of the \emph{long} GRB observations from 15 years of GBM catalogue with identified redshift, in which the GOLD sample contains 123 long GRBs at $z\le5.6$ and the FULL sample contains 151 long…

Cosmology and Nongalactic Astrophysics · Physics 2025-04-04 Huifeng Wang , Nan Liang

Gravitational lensing is a potentially powerful tool for elucidating the origin of gamma-ray emission from distant sources. Cosmic lenses magnify the emission from distance sources and produce time delays between mirage images.…

High Energy Astrophysical Phenomena · Physics 2015-08-19 Anna Barnacka , Margaret J. Geller , Ian P. Dell'Antonio , Wystan Benbow

We discuss the relation between cosmic-ray induced interstellar gamma-ray and radio emission from our Galaxy, and emphasize the importance of their parallel study. We give an overview of results from Fermi-LAT on the interstellar gamma-ray…

High Energy Astrophysical Phenomena · Physics 2015-06-15 Elena Orlando , Andrew W. Strong

We try to interpret the recently updated measurement of the cosmic ray electron (CRE) spectrum observed by Fermi-LAT, together with PAMELA data on positron fraction, in a single-component scenario adopting different propagation setups; we…

High Energy Astrophysical Phenomena · Physics 2022-03-02 Giuseppe Di Bernardo , Carmelo Evoli , Daniele Gaggero , Dario Grasso , Luca Maccione , Mario N. Mazziotta

Various studies firmly establish the fact that gamma-ray observations can act as a unique probe to detect the possible cosmic ray (CR) sources, study the CR density distribution and explore the average properties of interstellar medium…

High Energy Astrophysical Phenomena · Physics 2020-01-08 Sayan Biswas , Nayantara Gupta

The origin of the diffuse extragalactic gamma-ray background, which was measured with the large area telescope (LAT) aboard the Fermi satellite at energy below 820 GeV, and of the diffuse cosmic background of neutrinos, which was observed…

High Energy Astrophysical Phenomena · Physics 2015-05-21 Shlomo Dado , Arnon Dar

Decaying dark matter particles could be indirectly detected as an excess over a simple power law in the energy spectrum of the diffuse extragalactic gamma-ray background. Furthermore, since the Earth is not located at the center of the…

High Energy Physics - Phenomenology · Physics 2014-11-20 Alejandro Ibarra , David Tran , Christoph Weniger

The Large Area Telescope (LAT) aboard the $Fermi$ spacecraft routinely observes high-energy emission from gamma-ray bursts (GRBs). Here we present the second catalog of LAT-detected GRBs, covering the first 10 years of operations, from 2008…

High Energy Astrophysical Phenomena · Physics 2019-06-28 M. Axelsson , E. Bissaldi , N. Omodei , G. Vianello

In our previous work, we have investigated Galactic cosmic ray (GCR) spectra and anisotropy from 100 GeV to PeV, under anisotropic propagation model with axisymmetric distributed galactic sources. Numerous observational evidence have…

High Energy Astrophysical Phenomena · Physics 2024-12-24 Aifeng Li , Zhaodong Lv , Wei Liu , Yiqing Guo , Fangheng Zhang

The spatial diffusion of energetic particles in a magnetic field composed of a large-scale background and a small-scale turbulent component should be expected to be anisotropic. While such anisotropic diffusion has been known for quite a…

High Energy Astrophysical Phenomena · Physics 2025-07-17 Julien Dörner , Jonas Hellrung , Julia Becker Tjus , Horst Fichtner

Diffuse gamma-ray emission arising from interactions of cosmic rays with the interstellar gas traces the densities of both of them throughout the Milky Way. We discuss the results obtained from the analysis of Fermi LAT observations in the…

High Energy Astrophysical Phenomena · Physics 2019-08-14 L. Tibaldo , I. A. Grenier