Kumar, P.Narayan, RameshJohnson, J. L.2016-09-132008Kumar, P., R. Narayan, and J. L. Johnson. 2008. “Properties of Gamma-Ray Burst Progenitor Stars.” Science 321 (5887) (July 18): 376–379. doi:10.1126/science.1159003.0036-8075http://nrs.harvard.edu/urn-3:HUL.InstRepos:28487583We determine some basic properties of stars that produce spectacular gammaray 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) × 1010 cm, and that of the stellar envelope to be ∼ (1−2)×1011 cm. The density profile in the envelope is fairly shallow, with ρ ∼ r −2 . The rotation speeds of the core and envelope are ∼ 0.05 and ∼ 0.2 of the local Keplerian speed, respectively.en-USJournal Article2016-09-1310.1126/science.1159003