paper

The X-Ray Characteristics of a Classical Gamma-Ray Burst and its Afterglow

arXiv:astro-ph/9802055 · doi:10.1086/305815

Abstract

The serendipitous observation of GRB 780506 by co-aligned gamma-ray (HEAO 1 A-4 0.02 - 6 MeV) and X-ray (HEAO 1 A-2 2-60 keV) instruments during a six hour pointing at a blank section of the sky gave us unprecedented high signal-to-noise X-ray spectra and light curves of a gamma-ray burst and its afterglow. We observed two breaks in the initial spectrum, one consistent with a peak in nu-F-nu of ~45 keV, and one below 4 keV, consistent with strong absorption, followed by dramatic spectral variability. The initial strong turnover below a few keV evolved into a slight excess. The spectral shape varied widely outside low energy limits prescribed by current relativistic shock models. Two minutes after the burst ended, HEAO 1 A-2 detected a faint resurgence of 2-10 keV flux, rising to a peak ~seven minutes after burst onset, followed by irregular emission with best-fit decay time of half an hour. We estimated that this entire afterglow radiated between 3 and 30% of the >1 keV energy radiated during the burst.

45 pages, 18 of which are figures. References corrected, figures clarified, minor wording changes, to correspond to the form in which it will appear in the Astrophysical Journal, July 1, 501. Contains a detailed Appendix on a Bayesian Method for finding the position of a variable source

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