Luminous Late-time Radio Emission from Supernovae Interacting with Circumbinary Material

TL;DR

This paper models late-time radio emissions from supernovae interacting with circumbinary material formed by binary star mass transfer, explaining observed bright radio signals years after explosion.

Contribution

It introduces a forward modeling approach to link binary star mass transfer processes with observable late-time radio emissions in supernovae.

Findings

Dense CSM can be formed by non-conservative mass transfer in binaries.

Predicted radio luminosities match observed late-time emissions.

Complex early-time light curves can result from CSM geometry and velocity.

Abstract

Numerous core-collapse supernovae (CCSNe) exhibit signatures of interaction with circumstellar material (CSM). Bright radio emission years after the SN is one such indication of dense CSM at large distances from the star, which may be generated via binary interactions. In this work, we use forward modeling to study the radio emission produced by interaction between the SN ejecta and CSM formed by non-conservative stable mass transfer from stripped-envelope stars in short-period binaries. The donors are among the likely progenitors of hydrogen-poor CCSNe that significantly expand $10^3$-$10^4$ years before core-collapse, with companions that best represent low-mass compact objects. We identify that non-conservative stable mass transfer from lower-mass stripped stars can create a detached shell-like CSM, whereas for our higher-mass stars the CSM is wind-like. In our models, mass transfer rates of $\sim 10^{-4} M_\odot$ $\mathrm{yr}^{-1}$ lead to dense CSM extending to $\sim 10^{18}$ $\mathrm{cm}$. The predicted radio emission is luminous at late times, reaching $L_{\nu}\sim10^{26}$-$10^{29}\mathrm{erg}$ $\mathrm{s}^{-1}\mathrm{Hz}^{-1}$ at years to decades after core-collapse, which is as bright as late-time radio emission observed for a sample of hydrogen-poor SNe. However, the light curves of events with early-time data show more complex behavior in the weeks to months after core-collapse. We qualitatively demonstrate that similar early-time emission can manifest for CSM that is accelerated to speeds of $\sim10^3$ $\mathrm{km}$ $\mathrm{s}^{-1}$ upon ejection, as well as for different viewing angles in case of an asymmetric CSM distribution.