相关论文: Compton-induced $\gamma$-ray Cascade Emissions in …
Recent blazar detections by HESS, MAGIC, and VERITAS suggest that very-high-energy (VHE, E > 100 GeV) gamma-rays may be produced in most, if not all, types of blazars, including those that possess intense circumnuclear radiation fields. In…
The discovery of very-high-energy (VHE, E > 100 GeV) gamma-ray emission from intermediate- and low-frequency peaked blazars suggests that gamma-gamma absorption and pair cascading might occur in those objects. In previous papers, we…
Recent detections of very-high-energy (VHE, E > 100 GeV) gamma-ray blazars which do not belong to the high frequency peaked BL Lac (HBL) class, suggest that gamma-gamma absorption and pair cascading might occur in those objects. In the…
The radio galaxy NGC 1275, recently identified as a very high energy (VHE, >100 GeV) gamma-ray emitter by MAGIC, is one of the few non-blazar AGN detected in the VHE regime. In order to better understand the origin of the gamma-ray emission…
The radio galaxy NGC 1275, located at the central region of Perseus cluster, is a well-known very high-energy (VHE) gamma-ray emitter. The Major Atmospheric Cherenkov Experiment Telescope has detected two distinct episodes of VHE (E > 80…
Astrophysical models for the high-energy emission of blazars are reviewed. Blazars ejecting relativistic radio jets at small angles to the line-of-sight are the only type of active galactic nuclei (AGN) discovered above 100 MeV. The…
Recent high energy gamma-ray observations (E>100 MeV) of blazar AGN show emission spectra with no clear upper energy cutoff. AGN, considered to be possible sources for the highest energy cosmic rays, may have emission extending well into…
Emission from the active nucleus in the core of the brightest cluster galaxy of the Perseus cluster, NGC 1275, has varied dramatically over the past four decades. Prompted by the Fermi detection of flaring in the gamma-ray band, we present…
Previously unremarkable, the extragalactic radio source GB 1310+487 showed a gamma-ray flare on 2009 November 18, reaching a daily flux of ~10^-6 photons/cm^2/s at energies E>100 MeV and becoming one of the brightest GeV sources for about…
Recent data from the \emph{Fermi} Large Area Telescope have revealed about a dozen distant hard-spectrum blazars that have very-high-energy (VHE; $\gtrsim 100$ GeV) photons associated with them, but most of them have not yet been detected…
We report on the detection of very-high energy (VHE, E>100 GeV) gamma-ray emission from NGC 1275, the central radio galaxy of the Perseus cluster of galaxies. The source has been detected by the MAGIC telescopes with a statistical…
The Compton Gamma-Ray Observatory (CGRO) experiments EGRET and COMPTEL observed the Virgo sky region continuously for 7 weeks between December 10, 1996 and January 28, 1997. The prominent quasar 3C~273 was found to be the brightest source…
We present a statistical characterization of the $\gamma$-ray emission from the four \emph{Fermi}-LAT sources: FR I radio galaxy NGC 1275, BL Lac Mrk 421, FSRQs B2 1520+31 and PKS 1510-089 detected almost continuously over a time…
We report on our study of the high-energy $\gamma-$ray emission from the FR I radio galaxy NGC 1275, based on two years of observations with the Fermi-LAT detector. Previous Fermi studies of NGC 1275 had found evidence for spectral and flux…
The growing number of extragalactic high-energy (HE, E > 100 MeV) and very-high-energy (VHE, E > 100 GeV) gamma-ray sources that do not belong to the blazar class suggests that VHE gamma-ray production may be a common property of most…
The radio galaxy NGC 1275 is the Brightest Cluster Galaxy in the Perseus cluster. It is well-studied across all wavebands, including Very High Energy (VHE; E>100GeV gamma-rays, and with radio observations over the last 20 years tracking an…
We present a search for magnetically broadened gamma-ray emission around active galactic nuclei (AGN), using VERITAS observations of seven hard-spectrum blazars. A cascade process occurs when multi-TeV gamma rays from AGN interact with…
Radio and gamma-ray emission from active galactic nuclei (AGN) are thought to share a common origin, related to the ejection phenomena in the vicinity of supermassive black holes. Thanks to its sensitivity, surveying capability, and broad…
New high energy emission features have been recently discovered by the Cherenkov telescopes from active galaxies e.g., a few minutes variability time scale of TeV emission from Mrk 501 and PKS 2155-304, sub-TeV $\gamma$-ray emission from…
Context: Very-high-energy (VHE; E>100 GeV) {\gamma}-ray emission from blazars inevitably gives rise to electron-positron pair production through the interaction of these {\gamma}-rays with the Extragalactic Background Light (EBL). Depending…