Population Synthesis Study on the Binary Origin of Type Ibn Supernovae

TL;DR

This study uses binary population synthesis to evaluate the origins of Type Ibn supernovae, finding low-mass helium star binaries can explain observed rates, while mergers contribute less.

Contribution

It provides the first quantitative assessment of binary channels for Type Ibn supernovae using rapid population synthesis models.

Findings

Low-mass He star binaries can account for observed SN Ibn rates.

Mergers likely contribute only a fraction of SN Ibn events.

Typical companions are massive main sequence stars, with some white dwarf binaries having long delay times.

Abstract

Type Ibn supernovae (SNe) are a class of SN explosions whose progenitors are surrounded by dense helium-rich circumstellar matter (CSM). Some models have been proposed for how to form the dense CSM, with promising scenarios involving either binaries with a low-mass ($\lesssim 3~M_\odot$) helium (He) star, or mergers following common envelope phases between a He star and a compact object. Using rapid binary population synthesis calculations, we estimate the event rate of these channels and compare it with the observed SN Ibn rate. We find that exploding low-mass He stars in close binaries (of separations $\lesssim$ a few 100 $R_\odot$) can be sufficiently produced to account for the observed event rate of SN Ibn, while the merger scenario can likely account for only a fraction of these SNe. We discuss the types of companions expected in the low-mass He star scenario, finding massive main sequence stars ($10$--$20\ M_\odot$) to be typical, with a potentially non-negligible fraction ($<10\%$) of binaries with white dwarf (WD) companions that have long delay times of up to $100$ Myrs.