Models of bright nickel-free supernovae from stripped massive stars with circumstellar shells

TL;DR

This paper investigates bright, rapidly fading supernovae from stripped massive stars with circumstellar shells, proposing shock cooling and fallback of nickel as key mechanisms, supported by hydrodynamics and radiation transport models.

Contribution

It introduces a model for bright, rapidly fading supernovae originating from hydrogen-free massive stars with circumstellar shells, emphasizing shock cooling and fallback effects as novel explanations.

Findings

Circumstellar envelope properties significantly influence light curve diversity.

Fallback of stellar layers can remove radioactive nickel, explaining rapid decline.

Scaling relations connect supernova properties with circumstellar and explosion parameters.

Abstract

The nature of an emerging class of rapidly fading supernovae (RFSNe)--characterized by their short-lived light curve duration, but varying widely in peak brightness--remains puzzling. Whether the RFSNe arise from low-mass thermonuclear eruptions on white dwarfs or from the core collapse of massive stars is still a matter of dispute. We explore the possibility that the explosion of hydrogen-free massive stars could produce bright but rapidly fading transients if the effective pre-supernova radii are large and if little or no radioactive nickel is ejected. The source of radiation is then purely due to shock cooling. We study this model of RFSNe using spherically symmetric hydrodynamics and radiation transport calculations of the explosion of stripped stars embedded in helium-dominated winds or shells of various masses and extent. We present a parameter study showing how the properties of the circumstellar envelopes affect the dynamics of the explosion and can lead to a diversity of light curves. We also explore the dynamics of the fallback of the innermost stellar layers, which might be able to remove radioactive nickel from the ejecta, making the rapid decline in the late time light curve possible. We provide scaling relations that describe how the duration and luminosity of these events depend on the supernova kinetic energy and the mass and radius of the circumstellar material.