Related papers: The beaming effect and $\rm{\gamma}$-ray emission …
We report on measurements of the cosmic-ray induced gamma-ray emission of Earth's atmosphere by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. The LAT has observed the Earth during its commissioning phase and with a…
The curvature of the $\gamma$-ray spectrum in blazars may reflect the intrinsic distribution of the emitting electron distribution, which will further give some information on the possible acceleration and cooling processes in the emitting…
We present $\gamma$-ray, X-ray, ultraviolet, optical, and near-infrared light curves of 33 $\gamma$-ray bright blazars over four years that we have been monitoring since 2008 August with multiple optical, ground-based telescopes and the…
Observations of high energy emission from gamma-ray bursts (GRBs) constrain the extreme physical conditions associated with these energetic cosmic explosions. The Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope, a…
Long gamma-ray bursts (GRBs) have been suggested to occur preferentially in low metallicity environment. We discuss the possibility and theoretical aspects of using Lyman alpha emission properties of long GRB host galaxies as a metallicity…
A recent progress in the study of $\gamma$-ray jets is reviewed, with a focus on some theoretical interpretations of the VHE emission from M87, and possibly other misaligned blazars; the connection betwe en the GeV breaks exhibited by…
Recent observations of blazars at high energy (HE, 0.1-100 GeV) and very high energy (VHE, >0.1 TeV) have provided important constraints on the intensity and spectrum of the diffuse Extragalactic Background Light (EBL), shedding light on…
Blazars constitute the most enigmatic class of extragalactic gamma-ray sources, and their observational features have been ascribed to a relativistic jet closely aligned to the line of sight. They are generally divided in two main classes:…
We present the first measurement of the projected correlation function of 485 gamma-ray selected Blazars, divided in 175 BLLacertae (BL Lacs) and 310 Flat Spectrum Radio Quasars (FSRQs) detected in the 2-year all-sky survey by Fermi-Large…
Fermi has provided the largest sample of gamma-ray selected blazars to date. In this work we use a uniformly selected set of 211 BL Lacertae (BL Lac) objects detected by it Fermi during its first year of operation. We have obtained redshift…
Recent observations of Gamma-Ray Bursts (GRBs) by the Fermi Large Area Telescope (LAT) revealed a power law decay feature of the high energy emission (above 100 MeV), which led to the suggestion that it originates from a (probably…
The spectral properties from radio to optical bands are compared between the 18 optically bright Gamma-ray burst afterglows and well established power-spectrum sequence in Blazars. The comparison shows that the afterglows are well agreement…
Flat Spectrum Radio Quasars (FSRQs) and BL Lac objects detected in the first three months of the Fermi survey neatly separate in the gamma-ray spectral index vs gamma-ray luminosity plane. BL Lac objects are less luminous and have harder…
We present the results of studying the accretion disk vs jet power for a large fraction of all the blazars detected by the Fermi Gamma-Ray Space Telescope. The disk power is inferred from the emission line luminosities obtained from…
The availability of about a decade of uninterrupted sky monitoring by the Fermi satellite has made possible to study long-term quasi-periodicities for high-energy sources. It is therefore not a surprise that for several blazars in the…
If gamma ray bursts are highly collimated, the energy requirements of each event may be reduced by several (~ 4-6) orders of magnitude, and the event rate increased correspondingly. Extreme conditions in gamma ray bursters lead to highly…
...The distribution of radio core-dominance is consistent with average projection angles of 13.5, 14.8, 16.8, 20.4, and 28.2 for ISPs, LSPs, FSRQs, HSPs, and radio galaxies, respectively. Linear regression analyses of our data yield…
I present the results of a new approach to the intensity and photon density spectrum of the intergalactic background light as a function of redshift using observational data obtained in many different wavelength bands from local to deep…
Cosmic rays (CRs) can be studied through the galaxy-wide gamma-ray emission that they generate when propagating in the interstellar medium. The comparison of the diffuse signals from different systems may inform us about the key parameters…
Recent studies have found a positive correlation between the star-formation rate of galaxies and their gamma-ray luminosity. Galaxies with a high star-formation rate are expected to produce a large amount of high-energy cosmic rays, which…