Stellar Binary Companions to Supernova Progenitors

TL;DR

This paper discusses the prevalence and observational signatures of binary companions to supernova progenitors, highlighting how these secondaries can inform us about the progenitors' properties and the supernova remnants.

Contribution

It provides a comprehensive analysis of the observational consequences of binary companions to supernova progenitors, including signatures and implications for different supernova types.

Findings

50-70% of core-collapse supernova progenitors are in binaries.

Secondary stars often dominate optical light in Type Ib/c supernovae.

Bright secondaries produce identifiable blue-shifted absorption lines.

Abstract

For typical models of binary statistics, 50-70% of core-collapse supernova (ccSN) progenitors are members of a stellar binary at the time of the explosion. Independent of any consequences of mass transfer, this has observational consequences that can be used to study the binary properties of massive stars. In particular, the secondary companion to the progenitor of a Type Ib/c SN is frequently (~50%) the more optically luminous star since the high effective temperatures of the stripped progenitors make it relatively easy for a lower luminosity, cooler secondary to emit more optical light. Secondaries to the lower mass progenitors of Type II SN will frequently produce excess blue emission relative to the spectral energy distribution of the red primary. Available data constrain the models weakly. Any detected secondaries also provide an independent lower bound on the progenitor mass and, for historical SN, show that it was not a Type Ia event. Bright ccSN secondaries have an unambiguous, post-explosion observational signature - strong, blue-shifted, relatively broad absorption lines created by the developing supernova remnant. These can be used to locate historical SN with bright secondaries, confirm that a source is a secondary, and, potentially, measure abundances of ccSN ejecta. Luminous, hot secondaries will reionize the SNR on time scales of 100-1000 yrs that are faster than reionization by the reverse shock, creating peculiar HII regions due to the high metallicity and velocities of the ejecta.