An Excess of Mid-Infrared Emission from the Type Iax SN 2014dt

TL;DR

This paper reports the detection of a mid-infrared excess in SN 2014dt, suggesting the presence of newly formed dust or a dusty circumstellar medium, which provides insights into the progenitor system of Type Iax supernovae.

Contribution

It presents the first evidence of newly formed dust in a normal Type Ia supernova and discusses the implications for the progenitor system, including a possible single-degenerate origin.

Findings

Mid-IR excess observed in SN 2014dt nearly one year post-explosion.

The excess is consistent with 1E-5 M_solar of newly formed dust or a pre-existing dusty CSM.

The dust shell is less massive than those in other interacting supernovae.

Abstract

Supernovae Type Iax (SNe Iax) are less energetic and less luminous than typical thermonuclear explosions. A suggested explanation for the observed characteristics of this subclass is a binary progenitor system consisting of a CO white dwarf primary accreting from a helium star companion. A single-degenerate explosion channel might be expected to result in a dense circumstellar medium (CSM), although no evidence for such a CSM has yet been observed for this subclass. Here we present recent Spitzer observations of the SN Iax 2014dt obtained by the SPIRITS program nearly one year post-explosion that reveal a strong mid-IR excess over the expected fluxes of more normal SNe Ia. This excess is consistent with 1E-5 M_solar of newly formed dust, which would be the first time that newly formed dust has been observed to form in a normal Type Ia. The excess, however, is also consistent with a dusty CSM that was likely formed in pre-explosion mass-loss, thereby suggesting a single degenerate progenitor system. Compared to other SNe Ia that show significant shock interaction (SNe Ia-CSM) and interacting core-collapse events (SNe IIn), this dust shell in SN 2014dt is less massive. We consider the implications that such a pre-existing dust shell has for the progenitor system, including a binary system with a mass donor that is a red giant, a red supergiant, and an asymptotic giant branch star.