Journal Article

SN2019wxt: An Ultrastripped Supernova Candidate Discovered in the Electromagnetic Follow-up of a Gravitational Wave Trigger

Kasliwal, Mansi, Brightman, Murray, Shivkumar, Hinna, Carbone, Dario, Fremling, Christoffer, Tzanidakis, Anastasios, Désert, Jean-Michel, Corsi, Alessandra, Harrison, Fiona, Raaijmakers, Geert, A. J, Nayana, Jaodand, Amruta D, Madsen, Kristin Kruse, Nissanke, Samaya, Andreoni, Igor, Balasubramanian, Arvind

2023

Overview

We present optical, radio, and X-ray observations of a rapidly evolving transient SN2019wxt (PS19hgw), discovered during the search for an electromagnetic counterpart to the gravitational-wave (GW) trigger S191213g. Although S191213g was not confirmed as a significant GW event in the off-line analysis of LIGO-Virgo data, SN2019wxt remained an interesting transient due to its peculiar nature. The optical/near-infrared (NIR) light curve of SN2019wxt displayed a double-peaked structure evolving rapidly in a manner analogous to currently known ultrastripped supernovae (USSNe) candidates. This double-peaked structure suggests the presence of an extended envelope around the progenitor, best modeled with two components: (i) early-time shock-cooling emission and (ii) late-time radioactive 56Ni decay. We constrain the ejecta mass of SN2019wxt at M ej ≈ 0.20M ⊙, which indicates a significantly stripped progenitor that was possibly in a binary system. We also followed up SN2019wxt with long-term Chandra and Jansky Very Large Array observations spanning ∼260 days. We detected no definitive counterparts at the location of SN2019wxt in these long-term X-ray and radio observational campaigns. We establish the X-ray upper limit at 9.93 × 10−17 erg cm−2 s−1 and detect an excess radio emission from the region of SN2019wxt. However, there is little evidence for SN1993J- or GW170817-like variability of the radio flux over the course of our observations. A substantial host-galaxy contribution to the measured radio flux is likely. The discovery and early-time peak capture of SN2019wxt in optical/NIR observations during EMGW follow-up observations highlight the need for dedicated early, multiband photometric observations to identify USSNe.

• Publisher: IOP Publishing
• Subject: Ejecta / Galaxies / Gravitational waves / Light curve / Near infrared radiation / Photometric observations / Radio emission / Radioactive emissions / Supernova / Supernovae / Transients (astronomy) / X-ray astronomy / X-rays