The discovery by BeppoSAX and coordinated ground-based observations of persistent X-ray, visible and radio counterparts to GRB has successfully concluded a search begin in 1973, and the observed redshifted absorption lines have proved that GRB are at cosmological distances. The problem of explaining the mechanisms of GRB and their persistent counterparts remains. There are two classes of models...

We present a study of 15 long-duration γ-ray burst (GRB) host galaxies at z > 2. The GRBs are selected with available early-time afterglow spectra in order to compare interstellar medium (ISM) absorption-line properties with stellar properties of the host galaxies. In addition to five previously studied hosts, we consider new detections for the host galaxies of GRB 050820 and GRB 060206 and pla...

We show that the time variability of a gamma-ray burst (GRB) appears to be correlated with the absolute luminosity of the burst: smooth bursts are intrinsically less luminous. This Cepheid-like relationship can be used to determine the redshift of a GRB from parameters measured solely at gamma-ray energies. The relationship is based on only seven events at present and needs to be further confir...

The discovery by BeppoSAX and coordinated ground-based observations of persistent X-ray, visible and radio counterparts to GRB has successfully concluded a search begin in 1973, and the observed redshifted absorption lines have proved that GRB are at cosmological distances. The problem of explaining the mechanisms of GRB and their persistent counterparts remains. There are two classes of models...

— Highly variable γ-ray pulses and X-ray flares in GRB light curves can result from external shocks rather than central engine activity under the assumption that the GRB blast-wave shell does not spread. Acceleration of cosmic rays to > ∼ 10 eV energies can take place in the external shocks of GRBs. Escape of hadronic energy in the form of UHECRs leads to a rapidly decelerating GRB blast wave, ...

We consider the recent report that the supernova remnant W49B is a GammaRay Burst (GRB) remnant in our Galaxy. If this is correct, and if GRBs are sources of ultrahigh-energy cosmic rays (UHECRs), a natural consequence of this identification would be a detectable GeV-TeV photon emission around the GRB remnant. The imaging of the surrounding emission could provide new constraints on the jet stru...

The first well-localized short-duration gamma ray bursts (GRBs), GRB 050509b, GRB 050709 and GRB 050724, could have been the narrowly beamed initial spike of a burst/hyper flare of soft gamma ray repeaters (SGRs) in host galaxies at cosmological distances. Such bursts are expected if SGRs are young hyperstars, i.e. neutron stars where a considerable fraction of their neutrons have converted to ...

We present the extinction curves of long gamma ray burst (GRB) host galaxies (here after GRB hosts) utilizing the extinction feature of the optical afterglow of gamma ray bursts. The extinction curve of a galaxy is essential to understanding its dust and gas properties which in return will help us to reveal the origin of GRBs. We find out that the shape of the extinction curves may be divided i...

Tumors develop when infiltrating immune cells contribute growth stimuli, and cancer cells are selected to survive within such a cytotoxic microenvironment. One possible immune-escape mechanism is the upregulation of PI-9 (Serpin B9) within cancer cells. This serine proteinase inhibitor selectively inactivates apoptosis-inducing granzyme B (GrB) from cytotoxic granules of innate immune cells. We...