Observable fractions of core-collapse supernova light curves brightened by binary companions

TL;DR

This study estimates the fraction of core-collapse supernovae whose early light curves are brightened by binary companion collisions, finding it to be very small overall but more significant for Type Ibc supernovae, with implications for future surveys.

Contribution

The paper provides the first population synthesis estimate of observable supernova light-curve brightening due to binary companions, highlighting its rarity and potential for future detection.

Findings

0.19% of core-collapse supernovae show observable brightening

Type Ibc supernovae have a higher brightening fraction (~0.53%)

Future surveys may detect about 10 such events annually

Abstract

Many core-collapse supernova progenitors are presumed to be in binary systems. If a star explodes in a binary system, the early supernova light curve can be brightened by the collision of the supernova ejecta with the companion star. The early brightening can be observed when the observer is in the direction of the hole created by the collision. Based on a population synthesis model, we estimate the fractions of core-collapse supernovae in which the light-curve brightening by the collision can be observed. We find that 0.19% of core-collapse supernova light curves can be observed with the collisional brightening. Type Ibc supernova light curves are more likely to be brightened by the collision (0.53%) because of the high fraction of the progenitors being in binary systems and their proximity to the companion stars. Type II and IIb supernova light curves are less affected (~1e-3% and ~1e-2%, respectively). Although the early, slow light-curve declines of some Type IIb and Ibc supernovae are argued to be caused by the collision with the companion star (e.g. SN 2008D), the small expected fraction, as well as the unrealistically small separation required, disfavour the argument. The future transient survey by the Large Synoptic Survey Telescope is expected to detect ~10 Type Ibc supernovae with the early collisional brightening per year, and they will be able to provide information on supernova progenitors in binary systems.