A very low central oxygen mass in the peculiar type Ia SN 2010lp: further diversity at the low-luminosity end of SNe Ia

TL;DR

This study models the nebular spectrum of SN 2010lp, revealing an unusually low oxygen mass and double-peaked emission, suggesting a white dwarf merger origin and highlighting diversity in low-luminosity Type Ia supernovae.

Contribution

It provides the first detailed nebular spectral modeling of SN 2010lp, indicating a very low oxygen mass and supporting a merger scenario for this peculiar supernova.

Findings

Very low oxygen mass (~0.05 M_sun) in the ejecta

Double-peaked [OI] emission indicating asymmetric explosion

SN 2010lp may result from white dwarf merger or collision

Abstract

A nebular spectrum of the peculiar, low-luminosity type Ia supernova 2010lp is modelled in order to estimate the composition of the inner ejecta and to illuminate the nature of this event. Despite having a normally declining light curve, SN 2010lp was similar spectroscopically to SN 1991bg at early times. However, it showed a very unusual double-peaked [OI] $\lambda\lambda\,6300,6363$ emission at late times (Taubenberger et al. 2013). Modelling of the nebular spectrum suggests that a very small amount of oxygen ($\sim0.05$ M$_{\odot}$), expanding at very low speed ($\sim2000$ km/s) is sufficient to reproduce the observed emission. The rest of the nebula is not too dissimilar from SN 1991bg, except that SN 2010lp is slightly more luminous. The double-peaked [OI] emission suggests that SN 2010lp may be consistent with the merger or collision of two low-mass white dwarfs. The low end of the SN Ia luminosity sequence is clearly populated by diverse events, where different channels may contribute.