GRB 060218: A Relativistic Supernova Shock Breakout

• Published in: The Astrophysical journal 2007-09, Vol.667 (1), p.351-357
• Main Authors: Waxman, E, Mészáros, P, Campana, S
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/520715

We show that the prompt and afterglow X-ray emission of GRB 060218, as well as its early (l [unk] 1 day) optical-UV emission, can be explained by a model in which a radiation-mediated shock propagates outward from a compact progenitor star into a dense wind. The prompt thermal X-ray emission is produced in this model when the mildly relativistic shock, beta approximately 0.85, carrying a few times 10 super(49) erg, reaches the wind (Thomson) photosphere, where the postshock thermal radiation is released and the shock becomes collisionless. Adopting this interpretation of the thermal X-ray emission, we predict a subsequent X-ray afterglow, due to synchrotron emission and inverse Compton scattering of supernova UV photons by electrons accelerated in the collisionless shock. Early optical-UV emission is also predicted, due to the cooling of the outer delta M similar to 10 super(-8) M [unk] envelope of the star, which was heated to high temperature during the shock passage. The observed X-ray afterglow and the early optical-UV emission are both consistent with those expected in this model. Detailed analysis of the early optical-UV emission may provide detailed constraints on the density distribution near the stellar surface.