Circumstellar and explosion properties of Type Ibn supernovae

TL;DR

This study analyzes Type Ibn supernovae's light curves to understand their explosion and circumstellar properties, revealing differences from Type IIn SNe and suggesting distinct progenitor mass-loss behaviors.

Contribution

It provides the first detailed comparison of Type Ibn and Type IIn supernovae's circumstellar interactions and explosion parameters based on bolometric light curve analysis.

Findings

Type Ibn SNe are mainly powered by ejecta-CSM interaction.

Type Ibn SNe decline faster than Type IIn SNe, indicating earlier interaction cessation.

Type Ibn SNe may have smaller 56Ni mass and explosion energy, with possible fallback or non-terminal explosions.

Abstract

We investigate circumstellar and explosion properties of Type Ibn supernovae (SNe) by analyzing their bolometric light curves. Bolometric light curves of Type Ibn SNe generally have a large contrast between peak luminosity and late-phase luminosity, which is much larger than those of 56Ni-powered SNe. Thus, most of them are likely powered by the interaction between SN ejecta and dense circumstellar media. In addition, Type Ibn SNe decline much faster than Type IIn SNe, and this indicates that the interaction in Type Ibn SNe ceases earlier than in Type IIn SNe. Thus, we argue that Type Ibn SN progenitors experience high mass-loss rates in a short period just before explosion, while Type IIn SN progenitors have high mass-loss rates sustained for a long time. Furthermore, we show that rise time and peak luminosity of Type Ibn and Type IIn SNe are similar and thus, they have similar explosion properties and circumstellar density. The similar circumstellar density in the two kinds of SNe may indicate that mass-loss rates of Type Ibn SN progenitors are generally higher than those of Type IIn as the wind velocities inferred from narrow spectral components are generally higher in Type Ibn SNe. We also show that 56Ni mass and explosion energy of Type Ibn SNe may be smaller than those of other stripped-envelope SNe, probably because they tend to suffer large fallback or some of them may not even be terminal stellar explosions.