Aspherical Supernova Shock Breakout and the Observations of Supernova 2008D

Shock breakout is the earliest, readily-observable emission from a core-collapse supernova explosion. Observing supernova shock breakout may yield information about the nature of the supernova shock prior to exiting the progenitor and, in turn, about the core-collapse supernova mechanism itself. X-ray Outburst 080109, later associated with SN 2008D, is a very well-observed example of shock breakout from a core-collapse supernova. Despite excellent observational coverage and detailed modeling, fundamental information about the shock breakout, such as the radius of breakout and driver of the light curve time scale, is still uncertain. The models constructed for explaining the shock breakout emission from SN 2008D all assume spherical symmetry. We present a study of the observational characteristics of {\it aspherical} shock breakout from stripped-envelope core-collapse supernovae. We conduct two-dimensional, jet-driven supernova simulations from stripped-envelope progenitors and calculate the resulting shock breakout X-ray spectra and light curves. The X-ray spectra evolve significantly in time as the shocks expand outward and are not well-fit by single-temperature and radius black bodies. The time scale of the X-ray burst light curve of the shock breakout is related to the shock crossing time of the progenitor, not the much shorter light crossing time that sets the light curve time scale in spherical breakouts. This could explain the long shock breakout light curve time scale observed for XRO 080109/SN 2008D.