No Radio Afterglow from the Gamma - Ray Burst of February 28 , 1997

Spectral Properties of the Prompt X–ray emission and Afterglow from the Gamma–Ray Burst of 28 February 1997

We report high-energy spectral data of the prompt emission of GRB970228 and its X–ray afterglow. We establish that the nature of the X–ray afterglow emission is non-thermal and similar to the later portion of GRB970228. Our data can be used to discriminate different emission models of GRB afterglows. While cooling of excited compact objects can be ruled out, fireball models are constrained in t...

X–Ray Observations of γ–Ray Burst Afterglows

The discovery by the BeppoSAX satellite of X-ray afterglow emission from the γ-ray burst which occurred on 28 February 1997 produced a revolution in our knowledge of the γ-ray burst phenomenon. Along with the discovery of X-ray afterglows, the optical afterglows of γ-ray bursts were discovered and the distance issue was settled, at least for long γ-ray bursts. The 30 year mystery of the γ-ray b...

ar X iv : a st ro - p h / 97 06 06 5 v 1 6 J un 1 99 7 Discovery of the X - Ray Afterglow of the Gamma - Ray Burst of February 28 1997

The Rapidly Fading Afterglow from the Gamma - Ray Burst of 1999

We report on the discovery of the radio afterglow from the gamma-ray burst (GRB) of 1999 May 6 (GRB 990506) using the Very Large Array (VLA). The radio afterglow was detected at early times (∆t = 1.5 days), but began to fade rapidly sometime between 1 and 5 days after the burst. If we attribute the radio emission to the forward shock from an expanding fireball, then this rapid onset of the deca...

γ-ray burst after-glow: Confirming the cosmological fireball model

The recent detection of delayed X-ray and optical emission, “afterglow,” associated with γ-ray bursts (GRBs) supports models, where the bursts are produced by relativistic expanding blastwaves, “fireballs,” at cosmological distances. The detection of absorption lines in the optical afterglow of the GRB of 8 May 1997 confirms that the sources lie at cosmological distance. We show here that the n...