X-ray Observations of Two Type Ia Supernovae with an H$\alpha$ Line in their Optical Spectrum

TL;DR

This study used Chandra X-ray observations to investigate two low-luminosity Type Ia supernovae with early H$ extalpha$ lines, finding no X-ray emission and setting upper luminosity limits that inform about the surrounding environment.

Contribution

First X-ray observational constraints on low-luminosity Type Ia supernovae with early H$ extalpha$ lines, providing insights into their circumstellar environment and evolution.

Findings

No X-ray emission detected at supernova locations.

Upper luminosity limits are comparable to other low-luminosity Type Ia SNe.

The surrounding density likely decreased between optical and X-ray observations.

Abstract

We report on Chandra X-ray observations of SN 2016jae and SN 2018cqj, both low luminosity Type Ia supernova that showed the presence of a H line in their early optical spectrum. No X-ray emission is detected at the location of either SN. Upper limits to the luminosity of up to 2 $\times 10^{40}\,$ erg s$^{-1}$ are calculated for each SN, depending on the assumed spectral model, temperature and column density. This luminosity is comparable to that of another low-luminosity Type Ia SN, SN 2018fhw, that was observed with Chandra. It is generally lower than upper limits calculated for Type Ia-CSM SNe observed in X-rays, and also below that of SN 2012ca, the only Type Ia-CSM SN to have been detected in X-rays. Comparisons are made to other Type Ia SN with a H line observed in X-rays. The observations suggest that while the density into which the SN is expanding may have been high at the time the H$\alpha$ line was detected, it had decreased considerably by the time of X-ray observations.