GALEX Detection of Shock Breakout in Type II-P Supernova PS1-13arp: Implications for the Progenitor Star Wind

TL;DR

This paper reports the first GALEX detection of a UV shock breakout in a Type II-P supernova, revealing a prolonged emission likely caused by high pre-explosion mass loss in the progenitor star.

Contribution

It presents observational evidence of shock breakout in UV, indicating a prolonged duration due to stellar wind, and discusses implications for supernova progenitor mass-loss.

Findings

UV burst matches shock breakout predictions but lasts 50 times longer

Progenitor star experienced high mass-loss rate (~10^-3 Msun/yr)

Detection suggests future UV surveys can probe pre-supernova conditions

Abstract

We present the GALEX detection of a UV burst at the time of explosion of an optically normal Type II-P supernova (PS1-13arp) from the Pan-STARRS1 survey at z=0.1665. The temperature and luminosity of the UV burst match the theoretical predictions for shock breakout in a red supergiant, but with a duration a factor of ~50 longer than expected. We compare the $NUV$ light curve of PS1-13arp to previous GALEX detections of Type IIP SNe, and find clear distinctions that indicate that the UV emission is powered by shock breakout, and not by the subsequent cooling envelope emission previously detected in these systems. We interpret the ~ 1 d duration of the UV signal with a shock breakout in the wind of a red supergiant with a pre-explosion mass-loss rate of ~ 10^-3 Msun yr^-1. This mass-loss rate is enough to prolong the duration of the shock breakout signal, but not enough to produce an excess in the optical plateau light curve or narrow emission lines powered by circumstellar interaction. This detection of non-standard, potentially episodic high mass-loss in a RSG SN progenitor has favorable consequences for the prospects of future wide-field UV surveys to detect shock breakout directly in these systems, and provide a sensitive probe of the pre-explosion conditions of SN progenitors.