Accretion from a shock-inflated companion: double-peaked supernova lightcurve with periodic modulations

TL;DR

This paper proposes a model where neutron star accretion from a companion star causes periodic shock interactions, leading to a double-peaked supernova lightcurve with modulations, gamma-ray emission, and spectral features, explaining SN2022jli.

Contribution

It introduces a new scenario linking neutron star accretion and shock interactions to complex supernova lightcurve features and high-energy emissions.

Findings

Neutron star accretion occurs for binary separations less than 20 Rsun.

Shock heating causes periodic brightening and modulations in supernova lightcurves.

Model explains peculiar properties of SN2022jli, including double peaks and gamma-ray delays.

Abstract

We study the observational signatures from the interactions between a newly born neutron star and a companion star that is impacted by the supernova ejecta. We focus on the cases with bound post-explosion orbits, where the neutron star may periodically gravitationally capture gas from the companion. We find that neutron star accretion must occur if the pre-supernova binary separation is less than about 20 Rsun. This is because the stellar radius expands beyond this radius before the shock-inflated envelope undergoes Kelvin-Helmholtz contraction back to the main sequence. We then consider the internal shocks formed between adjacent episodes of disk wind. The shocks efficiently convert the wind kinetic energy into radiation (due to inverse-Compton cooling), which heats up the supernova ejecta located at much larger radii. The extra heating powers bright optical emission that is periodically modulated on the orbital timescale. The shocks also accelerate non-thermal particles which produce gamma-ray and neutrino emission from 100 MeV to 10 PeV via hardronic pp collisions. The high-energy photons leak out of the supernova ejecta after a delay of several months to one year. Photo-ionization of the slowest parts of the disk wind produces hydrogen recombination lines. We then use the model to explain the puzzling Type Ic supernova SN2022jli which shows a double-peaked optical lightcurve along with many peculiar properties, including delayed onset and rapid shutoff of the second peak, periodic modulations, delayed GeV emission, and narrow Balmer lines. Under this model, SN2022jli had a close-by companion at a pre-supernova binary separation of 10 to 20 Rsun, likely due to an earlier phase of common-envelope evolution.