Properties of Gamma-Ray Burst Progenitor Stars
Abstract
We determine some basic properties of stars that produce spectacular gamma-ray bursts at the end of their life. We assume that accretion of the outer portion of the stellar core by a central black hole fuels the prompt emission, and that fall-back and accretion of the stellar envelope later produces the plateau in the X-ray light curve seen in some bursts. Using X-ray data for three bursts we estimate the radius of the stellar core to be ~ 1-3 x 1010 cm, and that of the stellar envelope to be ~ 1-2 x 1011 cm. The density profile in the envelope is fairly shallow, with ~ r-2. The rotation speeds of the core and envelope are ~ 0.05 and ~ 0.2 of the local Keplerian speed, respectively.
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