SN 2018hna: 1987A-like supernova with a signature of shock breakout

TL;DR

This paper presents detailed multiwavelength observations and modeling of SN 2018hna, a peculiar Type II supernova similar to 1987A, revealing a blue supergiant progenitor with specific explosion parameters and low metallicity environment.

Contribution

It provides the first comprehensive observational and hydrodynamical analysis of SN 2018hna, highlighting its 1987A-like features and progenitor characteristics.

Findings

SN 2018hna exhibits a ~14-day cooling envelope phase after shock breakout.

The supernova has a rise time of ~88 days in the V-band, similar to SN 1987A.

Hydrodynamical modeling suggests a blue supergiant progenitor with radius ~50 R_sun.

Abstract

High cadence ultraviolet, optical and near-infrared photometric and low-resolution spectroscopic observations of the peculiar Type II supernova (SN) 2018hna are presented. The early phase multiband light curves exhibit the adiabatic cooling envelope emission following the shock breakout up to ~14 days from the explosion. SN~2018hna has a rise time of $\sim$\,88 days in the V-band, similar to SN 1987A. A $\rm^{56}Ni$ mass of ~0.087$\pm$0.004 $\rm M_{\odot}$ is inferred for SN 2018hna from its bolometric light curve. Hydrodynamical modelling of the cooling phase suggests a progenitor with a radius ~50 $\rm R_{\odot}$, a mass of ~14-20 $\rm M_{\odot}$ and explosion energy of ~1.7-2.9$\rm \times$ $\rm 10^{51}\ erg$. The smaller inferred radius of the progenitor than a standard red supergiant is indicative of a blue supergiant progenitor of SN 2018hna. A sub-solar metallicity (~0.3 $\rm Z_{\odot}$) is inferred for the host galaxy UGC 07534, concurrent with the low-metallicity environments of 1987A-like events.