OGLE-2013-SN-079: a lonely supernova consistent with a helium shell detonation

TL;DR

This paper reports on a peculiar supernova with unique spectral features, likely resulting from a helium shell detonation on a white dwarf, expanding understanding of supernova diversity and explosion mechanisms.

Contribution

It provides the first detailed observation of a Ti-dominated supernova spectrum, supporting helium shell detonation models.

Findings

Supernova has an absolute magnitude of about -17.6 in the I-band.

Spectra show Ti and Ca lines, with an unusually red color.

Data supports helium shell detonation and double-detonation models.

Abstract

We present observational data for a peculiar supernova discovered by the OGLE-IV survey and followed by the Public ESO Spectroscopic Survey for Transient Objects. The inferred redshift of $z=0.07$ implies an absolute magnitude in the rest-frame $I$-band of M$_{I}\sim-17.6$ mag. This places it in the luminosity range between normal Type Ia SNe and novae. Optical and near infrared spectroscopy reveal mostly Ti and Ca lines, and an unusually red color arising from strong depression of flux at rest wavelengths $<5000$ \AA. To date, this is the only reported SN showing Ti-dominated spectra. The data are broadly consistent with existing models for the pure detonation of a helium shell around a low-mass CO white dwarf and "double-detonation" models that include a secondary detonation of a CO core following a primary detonation in an overlying helium shell.