On the anomalous X-ray afterglows of GRB 970508 and GRB 970828

Abstract

Recently, BeppoSAX and ASCA have reported an unusual resurgence of soft X-ray emission during the afterglows of GRB 970508 and GRB 970828, together with marginal evidence for the existence of Fe-lines in both objects. We consider the implications of the existence of a torus of iron-rich material surrounding the sites of gamma ray bursts as would be expected in the SupraNova model; in particular, we show that the fireball will quickly hit this torus, and bring it to a temperature ~3x10^7 K. Bremsstrahlung emission from the heated up torus will cause a resurgence of the soft X-ray emission with all expected characteristics (flux level, duration and spectral hardening with time) identical to those observed during the reburst. Also, thermal emission from the torus will account for the observed iron line flux. These events are also observable, for instance by new missions such as SWIFT, when beaming away from our line sight makes us miss the main burst, as Fast (soft) X-ray Transients, with durations ~10^3 s, and fluences ~10^-7-10^-4 erg cm^-2. This model provides evidence in favor of the SupraNova model for Gamma Ray Bursts.

To appear in MN Pink pages, MN-LateX, no figures

Cited by in corpus (19)

• Gamma-Ray Bursts
• The Observed Offset Distribution of Gamma-Ray Bursts from Their Host Galaxies: A Robust Clue to the Nature of the Progenitors
• Galactic distribution of merging neutron stars and black holes - prospects for short GRB progenitors and LIGO/VIRGO
• Observation of X-ray lines from a Gamma-Ray Burst (GRB991216): Evidence of Moving Ejecta from the Progenitor
• Discovery of a redshifted Iron K-line in the X-ray afterglow of GRB 000214
• Iron K-alpha Emission from a Decaying Magnetar Model of Gamma-Ray Bursts
• Gamma-Ray Bursts: Afterglow Implications, Progenitor Clues and Prospects
• On the absorption feature in the prompt X-ray spectrum of GRB 990705
• The puzzling case of GRB 990123: prompt emission and broad-band afterglow modeling
• Off-Axis Neutrino Scattering in GRB Central Engines
• X-ray spectral features from GRBs: Predictions of progenitor models
• Line emission from gamma-ray burst environments
• X-ray Spectral Diagnostics of Gamma-Ray Burst Environments
• On the structure of the burst and afterglow of Gamma-Ray Bursts I: the radial approximation
• Thermal components in the early X-ray afterglow of GRBs
• A simple, stringent test on the nature of GRBs' progenitors
• A New Model for Iron Emission Lines and Re-Burst in GRB X-Ray Afterglows
• Specifying the Environments around GRB, Explaining the Fe line in the X-Ray Afterglow of GRB000214
• Possible geometries of afterglow generation in the gamma-ray burst GRB990705