Mass loss from Luminous Blue Variables and Quasi-Periodic Modulations of Radio Supernovae

TL;DR

This paper reviews mass loss in massive stars, highlighting its dependence on metallicity, and explores how LBV stars may cause observed radio supernova modulations, impacting models of gamma-ray bursts.

Contribution

It provides new insights into the metallicity dependence of WR star mass loss and links LBV mass-loss behavior to radio supernova modulations, suggesting LBVs as SN progenitors.

Findings

Strong metallicity dependence of WR mass loss at low metallicity.

Radio lightcurve modulations are consistent with LBV mass-loss patterns.

LBVs may be progenitors of some core-collapse supernovae.

Abstract

Massive stars, supernovae (SNe), and long-duration gamma-ray bursts (GRBs) have a huge impact on their environment. Despite their importance, a comprehensive knowledge of which massive stars produce which SN/GRB is hitherto lacking. We present a brief overview about our knowledge of mass loss in the Hertzsprung-Russell Diagram (HRD) covering evolutionary phases of the OB main sequence, the unstable Luminous Blue Variable (LBV) stage, and the Wolf-Rayet (WR) phase. Despite the fact that metals produced by ``self-enrichment'' in WR atmospheres exceed the initial -- host galaxy -- metallicity, by orders of magnitude, a particularly strong dependence of the mass-loss rate on the initial metallicity is found for WR stars at sub-solar metallicities (1/10 -- 1/100 solar). This provides a significant boost to the collapsar model for GRBs, as it may present a viable mechanism to prevent the loss of angular momentum by stellar winds at low metallicity, whilst strong Galactic WR winds may inhibit GRBs occurring at solar metallicities. Furthermore, we discuss recently reported quasi-sinusoidal modulations in the radio lightcurves of SNe 2001ig and 2003bg. We show that both the sinusoidal behaviour and the recurrence timescale of these modulations are consistent with the predicted mass-loss behaviour of LBVs, and we suggest LBVs may be the progenitors of some core-collapse SNe.