Helium giant stars as progenitors of rapidly fading Type Ibc supernovae

TL;DR

This paper proposes that helium giant stars with large radii can be progenitors of rapidly fading Type Ibc supernovae, explaining their shock-cooling light curves without significant nickel contribution.

Contribution

It introduces stellar models of helium giants that can produce RFSN light curves, highlighting a new progenitor scenario for these supernovae.

Findings

Helium giants with large radii can produce RFSN light curves upon explosion.

RFSNe may be distinguished from typical SNe Ibc by lack of radioactive nickel.

Large-radius helium stars are plausible progenitors for rapidly fading supernovae.

Abstract

Type I rapidly fading supernovae (RFSNe) appear to originate from hydrogen-free stars with large radii that produce predominantly shock-cooling light curves, in contrast with more typical nickel-rich SNe Ibc. However, it remains to be determined what types of stars would produce bright shock-cooling light curves without significant contribution from radioactive nickel. Bare helium stars in the mass range ~2-4 solar masses are known to hydrostatically develop radii as large as 100 solar radii or more due to strong He and C shell burning outside of a core with a sharp density gradient. We produce several such stellar models and demonstrate that, when exploded, these helium giants can naturally produce RFSN light curves. Since many prototypical SNe Ibc should come from large-radius stars in this mass range as well, we predict that these RFSNe may be distinct from SNe Ibc solely due to the absence of substantial nickel.