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


Abstract in English

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 $v_{s*}approx 2700-6000 ,rm km,s^{-1}$ ($E/Mapprox2-8times10^{50},rm erg/M_odot$) and one type IIb SN with $R_*approx210R_odot$ and $v_{s*}approx11000 rm, km,s^{-1}$ ($E/Mapprox1.8times10^{51},rm erg/M_odot$). 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.

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