Supernova Shock Breakout Through a Wind

TL;DR

This paper introduces a simple model to estimate supernova shock breakout conditions in a wind using observable X-ray flash data, providing insights into explosion parameters and shock velocities.

Contribution

The model relates observable X-ray flash properties to shock breakout conditions in supernovae exploding within winds, extending previous theories to include wind effects.

Findings

The model accurately constrains breakout radius, explosion energy, and ejecta mass for SN2008D.

It predicts high shock velocities consistent with observed non-thermal spectra.

Provides a framework for analyzing supernova shock breakouts in wind environments.

Abstract

The breakout of a supernova shock wave through the progenitor star's outer envelope is expected to appear as an X-ray flash. However, if the supernova explodes inside an optically-thick wind, the breakout flash is delayed. We present a simple model for estimating the conditions at shock breakout in a wind based on the general observable quantities in the X-ray flash lightcurve: the total energy E_X, and the diffusion time after the peak, t_diff. We base the derivation on the self-similar solution for the forward-reverse shock structure expected for an ejecta plowing through a pre-existing wind at large distances from the progenitor's surface. We find simple quantitative relations for the shock radius and velocity at breakout. By relating the ejecta density profile to the pre-explosion structure of the progenitor, the model can also be extended to constrain the combination of explosion energy and ejecta mass. For the observed case of XRO08109/SN2008D, our model provides reasonable constraints on the breakout radius, explosion energy, and ejecta mass, and predicts a high shock velocity which naturally accounts for the observed non-thermal spectrum.