The Type II-P Supernova 2019mhm and Constraints on Its Progenitor System

TL;DR

This paper studies the properties of supernova 2019mhm, including its explosion characteristics and progenitor star constraints, using pre- and post-explosion observations and modeling, to better understand Type II-P supernovae origins.

Contribution

It provides the first direct progenitor mass constraint for SN 2019mhm, combining Hubble imaging with supernova observations to refine progenitor mass estimates.

Findings

SN 2019mhm exhibits typical Type II-P spectral features and light curve.

Progenitor star mass estimated to be less than 17.5 solar masses.

No progenitor detected down to an absolute magnitude of -7.7 mag.

Abstract

We present pre- and post-explosion observations of the Type II-P supernova (SN~II-P) 2019mhm located in NGC~6753. Based on optical spectroscopy and photometry, we show that SN\,2019mhm exhibits broad lines of hydrogen with a velocity of $-8500\pm200$~km~s$^{-1}$ and a $111\pm2$~day extended plateau in its luminosity, typical of the Type II-P subclass. We also fit its late-time bolometric light curve and infer that it initially produced a ${}^{56}$Ni mass of $1.3 \times 10^{-2}$~M$_{\odot} \pm 5.5 \times 10^{-4}$~$M_\odot$. Using imaging from the Wide Field Planetary Camera 2 on the {\it Hubble Space Telescope} obtained 19~years before explosion, we aligned to a post-explosion Wide Field Camera 3 image and demonstrate that there is no detected counterpart to the SN to a limit of $>$24.53~mag in F814W, corresponding to an absolute magnitude limit of $M_{\rm F814W} < -7.7$~mag. Comparing to massive-star evolutionary tracks, we determine that the progenitor star had a maximum zero-age main sequence mass $<$17.5~M$_{\odot}$, consistent with other SN~II-P progenitor stars. SN\,2019mhm can be added to the growing population of SNe~II-P with both direct constraints on the brightness of their progenitor stars and well-observed SN properties.