Related papers: Maximum synchrotron frequency for shock-accelerate…
Fermi-type shear particle acceleration is a promising mechanism for sustaining ultra-relativistic particles along the kilo-parsec scale jets in Active Galactic Nuclei (AGNs). We explore the possibility of synchrotron-limited electron…
Gamma-ray bursts are produced by the dissipation of the kinetic energy of a highly relativistic fireball, via the formation of a collisionless shock. When this happens, Ultra High Energy Cosmic Rays up to 10^20 eV are produced. I show in…
It has been suggested that the prompt emission in gamma-ray bursts consists of several components giving rise to the observed spectral shape. Here we examine a sample of the 8 brightest, single pulsed {\it Fermi} bursts whose spectra are…
Electrons at the surface of a plasma that is irradiated by a laser with intensity in excess of $10^{23}~\mathrm{W}\mathrm{cm}^{-2}$ are accelerated so strongly that they emit bursts of synchrotron radiation. Although the combination of high…
We examine Fermi-type acceleration at relativistic shocks, and distinguish between the initial boost of the first shock crossing cycle, where the energy gain per particle can be very large, and the Fermi process proper with repeated shock…
The synchrotron cooling of relativistic electrons is one of the most effective radiation mechanisms in astrophysics. It not only accompanies the process of particle acceleration but also has feedback on the formation of the energy…
Gamma-ray bursts are generally considered to be the result of internal shocks generated in an inhomogeneous relativistic outflow that arises from a fireball. In such shocks, the Fermi acceleration of protons is naturally expected to be at…
In energetic nonthermal sources such as gamma-ray bursts, AGN or galactic jet sources, etc., one expects both relativistic and transrelativistic shocks acompanied by violent motions of moderately relativistic plasma. We present general…
Constraints on the diffusion and acceleration parameters in five young supernova remnants (SNRs) are derived from the observed thickness of their X-ray rims, as limited by the synchrotron losses of the highest energy electrons, assuming…
The energetic electromagnetic eruptions observed during the prompt phase of gamma-ray bursts are attributed to synchrotron emissions. The internal shocks moving through the ultrarelativistic jet, which is ejected by an imploding…
In most astrophysical processes involving synchrotron radiation, the pitch-angle distribution of the electrons is assumed to be isotropic. However, if electrons are accelerated anisotropically, e.g, in a relativistic shock wave with an…
Synchrotron radiation has markedly different behavior in $\sim 10~\textrm{keV}$ and in $\sim 100~\textrm{keV}$ plasma. We show that high-energy electrons which occupy the tail of velocity distribution function have disproportionate impact…
We model the emission of high energy photons due to relativistic charged particle motion in intense laser-plasma interactions. This is done within a particle-in-cell code, for which high frequency radiation normally cannot be resolved due…
Some recent experiments detecting very high energy (VHE) gamma-rays above 10-20 TeV independently reported VHE bursts for some of bright gamma-ray bursts (GRBs). If these signals are truly from GRBs, these GRBs must emit a much larger…
The emerging field of free-electron quantum optics enables electron-photon entanglement and holds the potential for generating nontrivial photon states for quantum information processing. Although recent experimental studies have entered…
Particle acceleration at magnetized purely perpendicular relativistic shocks in electron-ion plasmas are studied by means of two-dimensional particle-in-cell simulations. Magnetized shocks with the upstream bulk Lorentz factor $\gamma_1 \gg…
We examine 288 GRBs detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field-of-view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no…
Within the internal shock scenario we consider different mechanisms of high energy ($>1$ MeV) photon production inside a Gamma Ray Burst (GRB) fireball and derive the expected high energy photon spectra from individual GRBs during the…
The emission mechanism of the gamma-ray bursts (GRBs) is still a matter of debates. The standard synchrotron energy spectrum of cooling electrons F_E ~ E^{-1/2} is much too soft to account for the majority of the observed spectral slopes.…
We have calculated the opacities and secondary production mechanisms of high energy photons arising in gamma-ray burst internal shocks, using exact cross-sections for the relevant processes. We find that for reasonable choices of…