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Published Online June 26, 2008
Science DOI: 10.1126/science.1159003

Reports

Submitted on April 11, 2008
Accepted on June 17, 2008

Properties of Gamma-Ray Burst Progenitor Stars

Pawan Kumar 1*, Ramesh Narayan 2, Jarrett L. Johnson 1

1 Astronomy Department, University of Texas, Austin, TX 78712, USA.
2 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA.

* To whom correspondence should be addressed.
Pawan Kumar , E-mail: pk{at}astro.as.utexas.edu

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 {rho} ~ 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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Science. ISSN 0036-8075 (print), 1095-9203 (online)