Properties of Gamma-Ray Burst Progenitor Stars
Pawan Kumar,1*
Ramesh Narayan,2
Jarrett L. Johnson1
We determined some basic properties of stars that produce spectacular
gamma-ray bursts at the end of their lives. We assumed 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 produce the plateau
in the x-ray light curve seen in some bursts. Using x-ray data
for three bursts, we estimated the radius of the stellar core
to be
(1 – 3)
x 10
10 cm and that of the stellar envelope
to be
(1 – 2)
x 10
11 cm. The density profile in the envelope
is fairly shallow, with
r–2 (where
is density and
r is distance from the center of the explosion). The rotation
speeds of the core and envelope are
0.05 and
0.2 of the local
Keplerian speed, respectively.
2 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA.
* To whom correspondence should be addressed. E-mail: pk{at}astro.as.utexas.edu
