The GALEX-PTF experiment: II. supernova progenitor radius and energetics via shock-cooling modeling

TL;DR

This study uses early UV observations from GALEX and PTF to measure supernova progenitor radii and explosion energies, introducing a new modeling tool and highlighting the potential of UV surveys for supernova research.

Contribution

The paper presents a novel maximum likelihood fitting tool, SOPRANOS, for shock cooling models and applies it to early UV data to estimate supernova progenitor properties.

Findings

Progenitor radii range from 600 to 1100 R_sun for Type II SNe.

Shock velocities are estimated between 2700 and 6000 km/s.

One Type IIb SN has a progenitor radius of about 210 R_sun.

Abstract

The radius and surface composition of an exploding massive star, as well as the explosion energy per unit mass, can be measured using early ultraviolet (UV) observations of core-collapse supernovae (CC SNe). We present the results from a simultaneous \GALEX and Palomar Transient Factory (PTF) search for early UV emission from SNe. We analyze five CC SNe for which we obtained $NUV$ measurements before the first ground-based $R$-band detection. We introduce SOPRANOS, a new maximum likelihood fitting tool for models with variable temporal validity windows, and use it to fit the \citet{SapirWaxman2017} shock cooling model to the data. We report four Type II SNe with progenitor radii in the range of $R_*\approx600-1100R_\odot$ and a shock velocity parameter in the range of $v_{s*}\approx 2700-6000 \,\rm km\,s^{-1}$ ($E/M\approx2-8\times10^{50}\,\rm erg/M_\odot$) and one type IIb SN with $R_*\approx210R_\odot$ and $v_{s*}\approx11000 \rm\, km\,s^{-1}$ ($E/M\approx1.8\times10^{51}\,\rm erg/M_\odot$). Our pilot GALEX/PTF project thus suggests that a dedicated, systematic SN survey in the $NUV$ band, such as the wide-field UV explorer \textit{ULTRASAT} mission, is a compelling method to study the properties of SN progenitors and SN energetics.