Speaker
Description
The first detectable light of a supernova explosion is the shock breakout emission, which is produced as the supernova shock wave breaches the star's surface and which acts as a powerful diagnostic for the pre-explosion state of the progenitor system. I will discuss a novel way of categorizing the possible spectra observed immediately after breakout, and the recent advances in shock breakout theory underpinning this. We find that there are three important timescales controlling the spectral behavior: the light crossing time of the system, the initial diffusion time, and the time when the observer starts to see ejecta in thermal equilibrium. There are five allowed orderings of these timescales, each of which result in a different spectral evolution. Among these possibilities is a hitherto unexplored scenario, relevant to fast shocks breaking out from an extended envelope or circumstellar material, where thermalized ejecta are revealed in less than a light crossing time, resulting in a spectrum in which distinct blackbody and free-free emission components are blended together by light travel time effects. We apply this non-standard breakout scenario to explain the peculiar low-luminosity GRB 060218.
