2007/06/04 by Roger A. Chevalier, Chevalier, Roger A.
Medicine · Physics and Astronomy · #Astrophysics (astro-ph) #Autopsy Techniques and Outcomes #FOS: Physical sciences #Gamma-ray bursts and supernovae #astro-ph
paper · pdf · doi:10.48550/arxiv.0706.0461
15 pages, for "070228: The Next Decade of Gamma-Ray Burst Afterglows" eds. Wijers, R.A.M.J., Kaper, L, and van Eerten, H.J. (Elsevier: Amsterdam)
arxiv created 2007/06/04 · openalex publication_date 2007/06/04 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The association of long gamma-ray bursts (GRBs) with Type Ib/c supernovae implies that they explode into the winds of their Wolf-Rayet progenitor stars. Although the evolution of some GRB afterglows is consistent with expansion into a free wind, there is also good evidence for expansion into a constant density medium. The evidence includes the evolution of X-ray afterglows (when X-rays are below the cooling frequency), the evolution of the pre-jet break optical and X-ray afterglow, and the sharp turn-on observed for some afterglows. Recent observations of short bursts, which are expected to be interacting with a constant density medium, provide a check on the standard afterglow model. Although radio observations do not support the constant density model for long bursts in some cases, the evidence for constant density interaction is strong. The most plausible way to produce such a medium around a massive star is to shock the progenitor wind. This requires a smaller termination shock than would be expected, possibly due to a high pressure surroundings, a high progenitor velocity, or the particular evolution leading to a GRB. However, the need for the termination shock near the deceleration radius cannot be plausibly accomodated and may indicate that some long bursts have compact binary progenitors and explode directly into the interstellar medium.