The Intermediate Luminosity Optical Transient SN 2010da: The Progenitor, Eruption and Aftermath of a Peculiar Supergiant High-mass X-ray Binary

TL;DR

SN 2010da is a peculiar intermediate luminosity optical transient originating from a yellow supergiant star in NGC 300, exhibiting complex circumstellar environment, variability, and X-ray emission indicative of a compact companion.

Contribution

This study provides detailed multi-wavelength observations and analysis of SN 2010da, revealing its progenitor, eruption characteristics, and evidence of a high-mass X-ray binary system, which is a novel insight into such transients.

Findings

Progenitor is a 10-12 Msol yellow supergiant possibly in a blue loop phase.

SN 2010da had a peak magnitude of M<-10.4 mag, dimmer than typical ILOTs.

Detected complex circumstellar environment and X-ray emission indicating a compact companion.

Abstract

We present optical spectroscopy, ultraviolet to infrared imaging and X-ray observations of the intermediate luminosity optical transient (ILOT) SN 2010da in NGC 300 (d=1.86 Mpc) spanning from -6 to +6 years relative to the time of outburst in 2010. Based on the light curve and multi-epoch SEDs of SN 2010da, we conclude that the progenitor of SN 2010da is a ~10-12 Msol yellow supergiant possibly transitioning into a blue loop phase. During outburst, SN 2010da had a peak absolute magnitude of M<-10.4 mag, dimmer than other ILOTs and supernova impostors. We detect multi-component hydrogen Balmer, Paschen, and Ca II emission lines in our high-resolution spectra, which indicate a dusty and complex circumstellar environment. Since the 2010 eruption, the star has brightened by a factor of ~5 and remains highly variable in the optical. Furthermore, we detect SN 2010da in archival Swift and Chandra observations as an ultraluminous X-ray source (L~6x10^{39} erg/s). We additionally attribute He II 4686 Angstrom and coronal Fe emission lines in addition to a steady X-ray luminosity of ~10^{37} erg/s to the presence of a compact companion.