Early and Late-Time Observations of SN 2008ha: Additional Constraints for the Progenitor and Explosion

TL;DR

This paper presents early and late-time observations of SN 2008ha, providing new spectral evidence that supports its origin as a failed thermonuclear explosion of a white dwarf, distinguishing it from core-collapse supernovae.

Contribution

It offers the earliest spectrum of SN 2008ha showing intermediate mass elements and confirms its white dwarf origin through spectral features and late-time observations.

Findings

Detection of silicon, sulfur, and carbon features at maximum light.

Evidence of unburned material indicating a failed deflagration.

Late-time data consistent with a white dwarf explosion scenario.

Abstract

We present a new maximum-light optical spectrum of the the extremely low luminosity and exceptionally low energy Type Ia supernova (SN Ia) 2008ha, obtained one week before the earliest published spectrum. Previous observations of SN 2008ha were unable to distinguish between a massive star and white dwarf origin for the SN. The new maximum-light spectrum, obtained one week before the earliest previously published spectrum, unambiguously shows features corresponding to intermediate mass elements, including silicon, sulfur, and carbon. Although strong silicon features are seen in some core-collapse SNe, sulfur features, which are a signature of carbon/oxygen burning, have always been observed to be weak in such events. It is therefore likely that SN 2008ha was the result of a thermonuclear explosion of a carbon-oxygen white dwarf. Carbon features at maximum light show that unburned material is present to significant depths in the SN ejecta, strengthening the case that SN 2008ha was a failed deflagration. We also present late-time imaging and spectroscopy that are consistent with this scenario.