The supernova impostor PSN J09132750+7627410 and its progenitor

TL;DR

This study presents detailed optical observations of the supernova impostor PSN J09132750+7627410 over 250 days, revealing spectral features and identifying its progenitor as an 18-20 solar mass supergiant.

Contribution

It provides the first comprehensive spectroscopic monitoring of this impostor and identifies its progenitor star using archival Hubble Space Telescope data.

Findings

Spectroscopic data show narrow Balmer lines with P-Cygni profiles.

The transient's luminosity is typical for supernova impostors.

Archival images identify the progenitor as an 18-20 solar mass supergiant.

Abstract

We report the results of our follow-up campaign of the supernova impostor PSN J09132750+7627410, based on optical data covering $\sim250\,\rm{d}$. From the beginning, the transient shows prominent narrow Balmer lines with P-Cygni profiles, with a blue-shifted absorption component becoming more prominent with time. Along the $\sim3\,\rm{months}$ of the spectroscopic monitoring, broad components are never detected in the hydrogen lines, suggesting that these features are produced in slowly expanding material. The transient reaches an absolute magnitude $M_r=-13.60\pm0.19\,\rm{mag}$ at maximum, a typical luminosity for supernova impostors. Amateur astronomers provided $\sim4\,\rm{years}$ of archival observations of the host galaxy, NGC 2748. The detection of the quiescent progenitor star in archival images obtained with the Hubble Space Telescope suggests it to be an $18-20$\msun white-yellow supergiant.