Close, bright and boxy: the superluminous SN 2018hti

TL;DR

SN 2018hti is a nearby superluminous supernova with a slow rise, extremely bright peak, and possible powering mechanisms including magnetar activity or circumstellar interaction, originating from a massive progenitor.

Contribution

This study provides detailed light curve analysis and physical modeling of SN 2018hti, exploring its explosion mechanism and progenitor characteristics.

Findings

Luminosity rise time of ~50 days in rest frame.

Possible powering by magnetar or CSM interaction.

Progenitor star estimated at ~40 solar masses.

Abstract

SN 2018hti was a very nearby (z=0.0614) superluminous supernova with an exceedingly bright absolute magnitude of -21.7 mag in r-band at maximum. The densely sampled pre-maximum light curves of SN 2018hti show a slow luminosity evolution and constrain the rise time to ~50 rest-frame days. We fitted synthetic light curves to the photometry to infer the physical parameters of the explosion of SN 2018hti for both the magnetar and the CSM-interaction scenarios. We conclude that one of two mechanisms could be powering the luminosity of SN 2018hti; interaction with ~10 Msun of circumstellar material or a magnetar with a magnetic field of B_p~1.3e13 G and initial period of P_spin~1.8 ms. From the nebular spectrum modelling we infer that SN 2018hti likely results from the explosion of a ~40 Msun progenitor star.