Multidimensional Models of Type Ia Supernova Nebular Spectra: Strong Emission Lines from Stripped Companion Gas Rule Out Classic Single Degenerate Systems

TL;DR

This study uses advanced multidimensional spectral modeling to test the single-degenerate supernova progenitor model, finding that the predicted strong emission lines from stripped companion material are not observed, thus challenging this model.

Contribution

First multidimensional radiative transfer models of SNe Ia with stripped companion material, providing new constraints on progenitor systems based on nebular spectra.

Findings

Interaction models with main sequence companions produce detectable Hα emission, which is not observed.

Predicted He I emission lines offer additional observational diagnostics.

Stripped companion mass in SN 2011fe is constrained to less than 10^{-4} solar masses.

Abstract

The classic single-degenerate model for the progenitors of Type Ia Supernova (SN Ia) predicts that the supernova ejecta should be enriched with solar-like abundance material stripped from the companion star. Spectroscopic observations of normal SNe Ia at late times, however, have not resulted in definite detection of hydrogen. In this Letter, we study line formation in SNe Ia at nebular times using non-LTE spectral modeling. We present, for the first time, multidimensional radiative transfer calculations of SNe Ia with stripped material mixed in the ejecta core, based on hydrodynamical simulations of ejecta-companion interaction. We find that interaction models with main sequence companions produce significant H$\alpha$ emission at late times, ruling out this type of binaries being viable progenitors of SNe Ia. We also predict significant He I line emission at optical and near-infrared wavelengths for both hydrogen-rich or helium-rich material, providing an additional observational probe of stripped ejecta. We produce models with reduced stripped masses and find a more stringent mass limit of $M_{st} \lesssim 1\times 10^{-4} M_\odot$ of stripped companion material for SN 2011fe.