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

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