Related papers: Unexpected Dip in the Solar Gamma-Ray Spectrum
Novae have long been expected to be sources of emission at several MeV from the decay of radioactive elements in the novae ejecta, however, they were not anticipated to be sources of continuum emission in the GeV energy domain. In March…
The HAWC observatory recently published their second source catalog with 39 very high energy gamma-ray sources based on 507 days of exposure time. Among these, there were 16 sources that are more than one degree away from any known TeV…
Star clusters (SCs) are potential cosmic-ray (CR) accelerators and therefore are expected to emit high-energy radiation. However, a clear detection of gamma-ray emission from this source class has only been possible for a handful of cases.…
The Tibet ASgamma experiment just reported their measurement of sub-PeV diffuse gamma ray emission from the Galactic disk, with the highest energy up to 957 TeV. These gamma-rays are most likely the hadronic origin by cosmic ray interaction…
A deep observation campaign carried out by the High Energy Stereoscopic System (H.E.S.S.) on Centaurus A enabled the discovery of gamma rays from the blazar 1ES 1312-423, two degrees away from the radio galaxy. With a differential flux at 1…
The diffuse Galactic gamma-ray background, as observed with EGRET on CGRO, exceeds the model predictions significantly above 1 GeV. This is particularly true for the inner Galaxy. We shall discuss here the contribution of the Galactic…
The Milky Way's galactic center is a highly dynamical, crowded environment. Gamma ray observations of this region, such as the excess of GeV scale gamma rays observed by Fermi LAT, have been of tremendous interest to both the high energy…
One of the possible sources of hadronic cosmic rays (CRs) are newborn pulsars. If this is indeed the case, they should feature diffusive gamma-ray halos produced by interactions of CRs with interstellar gas. In this paper we try to identify…
Using 3.7 years of \Fermi-LAT data, we examine the diffuse 80-200 GeV emission in the inner Galaxy and find a resolved gamma-ray feature at $\sim 110-140$ GeV. We model the spatial distribution of this emission with a $\sim3\degree$ FWHM…
Astrophysical sources of nuclei are expected to produce a broad spectrum of isotopes, many of which are unstable. An unstable nucleus can beta-decay outside the source into a single-electron ion. Heavy one-electron ions, thus formed, can be…
The interpretation of gamma-ray emission originating from the solar disk ($0.5^\circ$ in angular size) as due to the interaction of Galactic Cosmic Rays (GCRs) with the solar atmosphere has remained a central challenge in solar physics.…
1ES 0414+009 (z = 0.287) is a distant high-frequency-peaked BL Lac object, and has long been considered a likely emitter of very-high energy (VHE, E>100 GeV) gamma-rays due to its high X-ray and radio flux. Observations in the VHE gamma-ray…
The recently discovered soft gamma-ray emission from the anomalous X-ray pulsar 1E 1841-045 has a luminosity L_g ~ 10^{36} ergs/s. This luminosity exceeds the spindown power by three orders of magnitude and must be fed by an alternative…
We report the detection of the lunar gamma-ray emission during the first year of Fermi-LAT observations. Such emission is produced by cosmic ray nuclei interacting with the lunar surface. Thanks to the solar minimum conditions and the…
The Fermi-LAT revealed that the census of the gamma-ray sky is dominated by blazars. Looking for a possible connection between radio and gamma-ray emission is a central issue for understanding the blazar physics, and various works were…
A number of Galactic sources emit GeV-TeV gamma rays that are produced through leptonic and/or hadronic mechanisms. Spectral analysis in this energy range is crucial in order to understand the emission mechanisms. The HAWC Gamma-Ray…
There is a growing new class of young spin-down powered pulsars called GeV-quiet soft gamma-ray pulsar; (1) spectral turnover appears around~10MeV, (2) the X-ray spectra of below 20 keV can be described by power law with photon index around…
Designed to be a successor of the previous flown space based gamma ray detectors, the Fermi Large Area Telescope (LAT) is also an electron detector. Taking advantage of its capability to separate electromagnetic and hadronic signals it is…
Diffuse $\gamma$-ray emission is the most prominent observable signature of celestial cosmic-ray interactions at high energies. While already being investigated at GeV energies over several decades, assessments of diffuse $\gamma$-ray…
We report on a detailed investigation of the gamma-ray emission from 18 broad line radio galaxies (BLRGs) based on two years of Fermi Large Area Telescope (LAT) data. We confirm the previously reported detections of 3C 120 and 3C 111 in the…