Helium superluminous SN 2021bnw : an explosion of a massive star with a pre-outburst

TL;DR

This study models the explosion of the helium-rich superluminous supernova 2021bnw, suggesting it was a core-collapse event of a massive star with specific ejecta and circumstellar matter properties, excluding a PPISN origin.

Contribution

The paper presents hydrodynamic and radiative-transfer simulations that fit the observed light curve of SLSN 2021bnw, proposing a core-collapse origin over a pulsational pair-instability scenario.

Findings

Best-fit model includes 15-22.5 Msun ejecta with 1.7 Msun of 56 Ni

Collision with 7 Msun circumstellar matter explains light curve

Excludes pulsational pair-instability as the explosion mechanism

Abstract

Superluminous supernovae (SLSNe) remain an intriguing topic in supernova (SN) transient astronomy. While the majority of SLSNe are shown to be explained by energy streaming from the newly born magnetar, there are others which are powered by different mechanisms. We analyse the pseudo-bolometric light curve of the nearby helium-rich SLSN 2021bnw. We built models and run hydrodynamics radiative-transfer simulations with STELLA. Our best-fit models include 15-22.5 Msun of ejecta enriched with 1.7 Msun of 56 Ni and carrying energy of 4 foe, and colliding w ith 7 Msun of circumstellar matter which match the observed light curve very well. The early data can be explained as cooling of an expanding shell with the mass of 0.5 Msun and kinetic energy of 0.7 foe. We tend to exclude a pulsational pair-instability (PPISN) origin for SLSN 2021bnw. Instead we conclude that SLSN 2021bnw was preferably a core-collapse explosion of a star with the initial mass of not less than 61 Msun aided by magnetorotational effects.