Light-curve and spectral properties of ultra-stripped core-collapse supernovae leading to binary neutron stars

TL;DR

This study models ultra-stripped supernovae resulting from binary star interactions, predicting their light curves and spectra, and compares these with observed transients to understand their role in forming binary neutron star systems.

Contribution

It provides detailed nucleosynthesis, light-curve, and spectral models for ultra-stripped supernovae, linking them to observed transients and estimating their contribution to neutron star binary formation.

Findings

Ultra-stripped supernovae produce ~0.01 Msun of 56Ni.

Their peak luminosity is around 10^42 erg/s (-16 mag).

Possible links to SN 2005ek, calcium-rich transients, and SN 2010X.

Abstract

We investigate light-curve and spectral properties of ultra-stripped core-collapse supernovae. Ultra-stripped supernovae are the explosions of heavily stripped massive stars which lost their envelopes via binary interactions with a compact companion star. They eject only ~ 0.1 Msun and may be the main way to form double neutron-star systems which eventually merge emitting strong gravitational waves. We follow the evolution of an ultra-stripped supernova progenitor until iron core collapse and perform explosive nucleosynthesis calculations. We then synthesize light curves and spectra of ultra-stripped supernovae using the nucleosynthesis results and present their expected properties. Ultra-stripped supernovae synthesize ~ 0.01 Msun of radioactive 56Ni, and their typical peak luminosity is around 1e42 erg/s or -16 mag. Their typical rise time is 5 - 10 days. Comparing synthesized and observed spectra, we find that SN 2005ek, some of the so-called calcium-rich gap transients, and SN 2010X may be related to ultra-stripped supernovae. If these supernovae are actually ultra-stripped supernovae, their event rate is expected to be about 1 per cent of core-collapse supernovae. Comparing the double neutron-star merger rate obtained by future gravitational-wave observations and the ultra-stripped supernova rate obtained by optical transient surveys identified with our synthesized light-curve and spectral models, we will be able to judge whether ultra-stripped supernovae are actually a major contributor to the binary neutron star population and provide constraints on binary stellar evolution.