The Type Ibn Supernova 2019kbj -- Indications for Diversity in Type Ibn Supernova Progenitors

TL;DR

This paper analyzes the light curve of the Type Ibn supernova 2019kbj, suggesting diversity in progenitor systems and explosion mechanisms, with circumstellar interaction playing a significant role in its luminosity.

Contribution

It models the light curve of SN 2019kbj to constrain progenitor and explosion parameters, highlighting diversity among Type Ibn supernovae.

Findings

Circumstellar material interaction powers the supernova luminosity.

SN 2019kbj has a uniform-density CSM shell with ~0.1 solar masses of Ni56.

Compared to SN 2019uo, SN 2019kbj shows different Ni56 and ejecta masses, indicating progenitor diversity.

Abstract

Type Ibn supernovae (SNe) are a rare class of stellar explosions whose progenitor systems are not yet well determined. We present and analyze observations of the Type Ibn SN 2019kbj, and model its light curve in order to constrain its progenitor and explosion parameters. SN 2019kbj shows roughly constant temperature during the first month after peak, indicating a power source (likely circumstellar material interaction) that keeps the continuum emission hot at ~15,000K. Indeed, we find that the radioactive decay of Ni56 is disfavored as the sole power source of the bolometric light curve. A radioactive decay + circumstellar-material (CSM) interaction model, on the other hand, does reproduce the bolometric emission well. The fits prefer a uniform-density CSM shell rather than CSM due to a steady mass-loss wind, similar to what is seen in other Type Ibn SNe. The uniform-density CSM shell model requires ~0.1 solar masses of Ni56 and ~1 solar mass of total ejecta to reproduce the light curve. SN 2019kbj differs in this manner from another Type Ibn SN with derived physical parameters, SN 2019uo, for which an order of magnitude lower Ni56 mass and larger ejecta mass were derived. This points towards a possible diversity in SN Ibn progenitor systems and explosions.