Asphericity in Supernova Explosions from Late-Time Spectroscopy

TL;DR

This study analyzes late-time spectra of core-collapse supernovae from stripped-envelope stars, revealing that all such supernovae are aspherical, with those linked to gamma-ray bursts showing the greatest asphericity.

Contribution

It provides evidence that asphericity is a universal feature in core-collapse supernovae from stripped-envelope stars, especially in those associated with gamma-ray bursts.

Findings

High incidence of double-peaked oxygen emission-line profiles

All observed supernovae from stripped-envelope stars are aspherical

Supernovae with gamma-ray bursts show the highest asphericity

Abstract

Core-collapse supernovae (CC-SNe) are the explosions that announce the death of massive stars. Some CC-SNe are linked to long-duration gamma-ray bursts (GRBs) and are highly aspherical. One important question is to what extent asphericity is common to all CC-SNe. Here we present late-time spectra for a number of CC-SNe from stripped-envelope stars, and use them to explore any asphericity generated in the inner part of the exploding star, near the site of collapse. A range of oxygen emission-line profiles is observed, including a high incidence of double-peaked profiles, a distinct signature of an aspherical explosion. Our results suggest that all CC-SNe from stripped-envelope stars are aspherical explosions and that SNe accompanied by GRBs exhibit the highest degree of asphericity.