Extreme mass loss in low-mass type Ib/c supernova progenitors

TL;DR

This paper investigates how extreme mass loss in low-mass helium star progenitors, driven by binary interactions, leads to dense circumstellar material, explaining observations of certain hydrogen-poor supernovae.

Contribution

It identifies a specific evolutionary pathway involving helium shell burning and binary mass transfer that produces dense CSM around low-mass helium stars before supernova.

Findings

Helium star envelopes expand significantly due to shell burning.

High mass transfer rates occur weeks to decades before collapse.

Resulting CSM properties match those inferred for ultra-stripped and type Ibn SNe.

Abstract

Many core collapse supernovae (SNe) with hydrogen-poor and low-mass ejecta, such as ultra-stripped SNe and type Ibn SNe, are observed to interact with dense circumstellar material (CSM). These events likely arise from the core-collapse of helium stars which have been heavily stripped by a binary companion and ejected significant mass during the last weeks to years of their lives. In helium star models run to days before core-collapse, we identify a range of helium core masses $\approx 2.5 -3 M_{\odot}$ whose envelopes expand substantially due to helium shell burning while the core undergoes neon and oxygen burning. When modeled in binary systems, the rapid expansion of these helium stars induces extremely high rates of late-stage mass transfer ($\dot{M} \gtrsim 10^{-2} M_\odot/{\rm yr}$) beginning weeks to decades before core-collapse. We consider two scenarios for producing CSM in these systems: either mass transfer remains stable and mass loss is driven from the system in the vicinity of the accreting companion, or mass transfer becomes unstable and causes a common envelope event (CEE) through which the helium envelope is unbound. The ensuing CSM properties are consistent with the CSM masses ($\sim 10^{-2}-1 M_\odot$) and radii ($\sim 10^{13}-10^{16} {\rm cm}$) inferred for ultra-stripped SNe and several type Ibn SNe. Furthermore, systems that undergo a CEE could produce short-period NS binaries that merge in less than 100 Myr.