Episodic modulations in supernova radio light curves from luminous blue variable supernova progenitor models

TL;DR

This study links luminous blue variable (LBV) progenitors to episodic modulations in supernova radio light curves, demonstrating that stellar wind density variations can cause observable radio flux fluctuations in certain supernovae.

Contribution

It provides a novel connection between LBV progenitors and radio light curve modulations, supported by stellar evolution models and circumstellar medium analysis.

Findings

20Msun model shows episodic radio luminosity modulations

25Msun model does not show such modulations

Episodic modulations are caused by wind density variations near the bistability limit

Abstract

<Context> Ideally, one would like to know which type of core-collapse SNe is produced by different progenitors and the channels of stellar evolution leading to these progenitors. These links have to be very well known to use the observed frequency of different types of SN events for probing the star formation rate and massive star evolution in different types of galaxies. <Aims> We investigate the link between LBV as SN progenitors and the appearance of episodic radio light curve modulations of the SN event. <Methods> We use the 20Msun and 25Msun models with rotation at solar metallicity, part of an extended grid of stellar models computed by the Geneva team. At their pre-SN stage, these two models have recently been shown to have spectra similar to those of LBV stars and possibly explode as Type IIb SNe. Based on the wind properties before the explosion, we derive the density structure of their circumstellar medium. This structure is used as input for computing the SN radio light curve. <Results> We find that the 20Msun model shows radio light curves with episodic luminosity modulations, similar to those observed in some Type IIb SNe. This occurs because the evolution of the 20Msun model terminates in a region of the HR diagram where radiative stellar winds present strong density variations, caused by the bistability limit. The 25Msun model, ending its evolution in a zone of the HR diagram where no change of the mass-loss rates is expected, presents no such modulations in its radio SN light curve. <Conclusions> Our results reinforce the link between SN progenitors and LBV stars. We also confirm the existence of a physical mechanism for a single star to have episodic radio light curve modulations. In the case of the 25Msun progenitors, we do not obtain modulations in the radio light curve, but our models may miss some outbursting behavior in the late stages of massive stars.