Mass loss of massive helium star supernova progenitors shortly before explosion constrained by supernova radio properties

TL;DR

This study uses radio observations of Type Ibc supernovae to constrain the mass-loss rates of their massive helium star progenitors, suggesting higher mass-loss rates than some models predict and indicating possible pre-explosion mass-loss enhancements.

Contribution

It provides observational constraints on helium star mass-loss rates before supernova explosions, challenging existing prescriptions and proposing alternative mass-loss mechanisms.

Findings

Mass-loss rates > 1e-6 Msun/yr are needed for typical Type Ibc progenitors.

Standard radiation-driven wind models may underestimate pre-supernova mass loss.

Pre-explosion mass-loss enhancement mechanisms are suggested.

Abstract

Mass loss of massive helium stars is not well understood even though it plays an essential role in determining their remnant neutron-star or black-hole masses as well as ejecta mass of Type Ibc supernovae. Radio emission from Type Ibc supernovae is strongly affected by circumstellar matter properties formed by mass loss of their massive helium star progenitors. In this study, we estimate the rise time and peak luminosity distributions of Type Ibc supernovae in radio based on a few massive helium star mass-loss prescriptions and compare them with the observed distribution to constrain the uncertain massive helium star mass-loss rates. We find that massive helium stars in the luminosity range expected for ordinary Type Ibc supernova progenitors (4.6 ~< log L/Lsun ~< 5.2) should generally have large mass-loss rates (> ~ 1e-6 Msun/yr) in order to account for the observed rise time and peak luminosity distribution. Therefore, mass-loss prescriptions that predict significantly low mass-loss rates for helium stars in this luminosity range is inconsistent with the supernova radio observations. It is also possible that massive helium stars shortly before their explosion generally undergo mass-loss enhancement in a different way from the standard radiation-driven wind mechanism.