Related papers: Light speed variation from active galactic nuclei
Radio-loud active galactic nuclei (AGN) are among the most luminous objects in the Universe, emitting radiation from low-energy radio waves to high energy $\gamma$-rays. They are well known to exhibit flux variations at nearly all…
Lorentz Invariance Violation (LIV) arises in various quantum-gravity theories. As the typical energy for quantum gravity is the Planck mass, $M_{pl}$, LIV will, most likely, be manifested at very high energies that are not accessible on…
It has been long conjectured that a signature of Quantum Gravity will be Lorentz Invariance Violation (LIV) that could be observed at energies much lower than the Planck scale. One possible signature of LIV is an energy-dependent speed of…
Some gamma-ray burst (GRB) spectra exhibit high energy tails with the highest photon energy detected at 18 GeV. The spectral slope of the high-energy tails is sufficiently flat in nu F_nu to consider the possibility of their detection at…
Adopting the hypothesis that the nonthermal emission of Active Galactic Nuclei (AGN) is primarily due to the acceleration of protons, we construct a simple model in which the interplay of acceleration and losses can be studied together with…
We predict a new class of very intense, short-duration AGN flares capable of accelerating the highest energy cosmic rays, resulting from the tidal disruption of a star or from a disk instability. The rate and power of these flares readily…
The recently discovered gamma-ray burst (GRB) GRB 060218/SN 2006aj is classified as an X-ray Flash with very long duration driven possibly by a neutron star. Since GRB 060218 is very near about 140 Mpc and very dim, one-year observation by…
Gamma-ray bursts (GRBs) rank among the most powerful astrophysical phenomena, characterized by complex and highly variable prompt emission light curves that reflect the dynamics of their central engines. In this work, we analyze a sample of…
The possible variation of the electromagnetic fine structure constant $\alpha_e$ on cosmological scales arouses great interests in recent years. The strongly lensed gravitational waves and the electromagnetic counterparts could be used to…
Gamma-ray bursts are the most concentrated explosions in the Universe. They have been detected electromagnetically at energies up to tens of GeV, and it is suspected that they could be active at least up to TeV energies. It is also…
The prompt emission of the gamma-ray bursts is found to be very energetic, releasing ~10^51 ergs in a flash. However, their emission mechanism remains unclear and understanding their spectra is a key to determining the emission mechanism.…
We present the light curves obtained during an eight-year program of optical spectroscopic monitoring of nine Seyfert 1 galaxies: 3C 120, Akn 120, Mrk 79, Mrk 110, Mrk 335, Mrk 509, Mrk 590, Mrk 704, and Mrk 817. All objects show…
The largest group of sources identified by EGRET are Blazars. This sub-class of AGN is well known to vary in flux in all energy bands on time-scales ranging from a few minutes (in the optical and X-ray bands) up to decades (radio and…
The observations suggest that $\gamma$-ray bursts (GRBs) are produced by jets of relativistic cannonballs (CBs), emitted in supernova (SN) explosions. The CBs, reheated by their collision with the SN shell, emit radiation and Doppler-boost…
The highest energy gamma-rays from gamma-ray bursts (GRBs) have important implications for their radiation mechanism. Here we report for the first time the detection of gamma-rays up to 13 TeV from the brightest GRB 221009A by the Large…
We present a new model for gamma-ray bursts (GRBs) that are not only associated with supernovae but also have small baryon contamination. In this model, we assume a newborn neutron star to move outward at a kick velocity of $\sim 10^3 {\rm…
Markarian 421 (Mrk 421) is a high-synchrotron-peaked blazar showing relentless variability across the electromagnetic spectrum from radio to gamma-rays. We use over 7-years of radio and GeV observations to study the correlation and…
Gamma-ray bursts (GRBs) are rare but powerful explosions displaying highly relativistic jets. It has been suggested that a significant fraction of the much more frequent core-collapse supernovae are accompanied by comparably energetic but…
Several models of Quantum Gravity predict Lorentz Symmetry breaking at energy scales approaching the Planck scale (10^{19} GeV). With present photon data from the observations of distant astrophysical sources, it is possible to constrain…
Both long and short gamma-ray bursts (GRBs) are expected to occur in the dense environments of active galactic nuclei (AGN) accretion disks. As these bursts propagate through the disks they live in, they photoionize the medium causing…