Related papers: GRBs, Fireballs and Precessing Gamma Jets
Gamma-ray bursts (GRBs) are the most luminous electromagnetic explosions in the Universe, which emit up to $8.8\times10^{54}$ erg isotropic equivalent energy in the hard X-ray band. The high luminosity makes them detectable out to the…
A possible unified model of short and long gamma-ray bursts (GRBs), X-ray rich GRBs, and X-ray flashes is proposed. It is assumed that the jet of a GRB consists of many emitting sub-shells (i.e., an inhomogeneous jet model). The…
Observational evidence of iron absorption and emission lines in X-ray spectra of Gamma-Ray Bursts is quite compelling. I will briefly review the results, summarize different models and describe the connection with massive progenitors in…
We discuss some open problems concerning the origin and the emission mechanism of gamma-ray bursts (GRBs) in light of recent developments. If GRBs originate at extragalactic distances, we are facing four crises: (1) an energy crisis, models…
We briefly discuss the theoretical implications of recent detections of gamma-ray bursts (GRBs) by BSAX. Relativistic shock wave theories of fireball expansion are challenged by the wealth of X-ray, optical and radio data obtained after the…
Gamma-ray bursts (GRBs) are the most luminous explosions in the universe, yet the nature and physical properties of their energy sources are far from understood. Very important clues, however, can be inferred by studying the afterglows of…
Knowledge of the bulk Lorentz factor $\Gamma_{0}$ of GRBs allows us to compute their comoving frame properties shedding light on their physics. Upon collisions with the circumburst matter, the fireball of a GRB starts to decelerate,…
Gamma-ray burst (GRB) engines are probed most intimately during the prompt gamma-ray luminous phase when the expanding blast wave is closest to the explosion center. Using GRBs 990123 and 940217 as guides, we briefly review observations of…
The most energetic gamma-ray bursts (GRBs) are remarkable sources releasing huge amounts of energy on short timescales. Their prompt emission, which usually lasts few seconds, is so bright that it is visible across the whole observable…
Gamma-ray bursts GRBs are among the most mysterious astronomical phenomenon ever discovered. Unlike most astronomical discoveries which were explained within weeks or months after their initial discovery, GRBs remain a puzzle for more than…
The recent years witnessed a dramatic improvement in our knowledge of the phenomenology and physics of Gamma Ray Bursts (GRBs). However, our "pillars of knowledge" remain a few, while many aspects remain obscure and not understood. There is…
We study a cosmological scenario for gamma ray bursts (GRBs) where relativistic flows interact with dense radiation fields. It is shown that this scenario is plausible in very dense stellar regions which are known to exist in collapsed…
If the threshold for $e^{-}e^{+}$ pair production depends on an angle between photon momenta, and if the $\gamma$-rays are collimated right in gamma-ray burst (GRB) source then another solution of the compactness problem is possible. The…
Recent observations suggest that gamma-ray bursts (GRBs) and their afterglows are produced by jets of highly relativistic cannonballs (CBs), emitted in supernova explosions. The fully ionized CBs cool to a temperature below 4500 K within a…
Long gamma-ray bursts (GRBs) are commonly accepted to originate in the explosion of particularly massive stars, which gives rise to a highly relativistic jet. Internal inhomogeneities in the expanding flow give rise to internal shock waves…
The origin of prompt emission in GRBs is not yet well understood. The simplest and most popular model is Synchrotron, Self-Compton (SSC) emission produced by internal shocks inside an ultra-relativistic jet. However, recent observations of…
The successful launch and operation of NASA's Swift Gamma-Ray Burst Explorer open a new era for the multi-wavelength study of the very early afterglow phase of gamma-ray bursts (GRBs). GRB early afterglow information is essential to explore…
Observations suggest that $\gamma$-ray bursts (GRBs) are produced by the dissipation of the kinetic energy of a relativistic fireball. We show that a large fraction, $\ge 10%$, of the fireball energy is expected to be converted by…
Whether gamma-ray bursts are highly beamed or not is a very important question, since it has been pointed out that the beaming will lead to a sharp break in the afterglow light curves during the ultra-relativistic phase, with the breaking…
The favored progenitor model for Gamma-ray Bursts (GRBs) with Supernova (SN) association is the core collapse of massive stars. One possible outcome of such a collapse is a rapidly spinning, strongly magnetized neutron star ("magnetar"). We…