The nearby He-rich superluminous supernova SN 2021bnw at photospheric phases

TL;DR

This paper analyzes the nearby helium-rich superluminous supernova SN 2021bnw, examining its light curves, spectra, and explosion physics to understand its unique properties and progenitor characteristics.

Contribution

It provides detailed spectro-photometric data and modeling of SN 2021bnw, highlighting the role of ejecta interaction with He-rich circumstellar material in powering the supernova.

Findings

SN 2021bnw reached -20.7 mag at maximum in g band.

Spectral analysis identified helium features at late phases.

Modeling suggests ejecta-CSM interaction as the main power source.

Abstract

Aim. We present and interpret the data of the nearby hydrogen-deficient but helium-rich superluminous supernova SN~2021bnw which reached a magnitude of -20.7 at maximum luminosity in g band. Methods. We discuss the light curves and spectra of SN 2021bnw based on its spectro-photometric follow up exploiting different observational facilities. We reproduce the NIR spectrum of SN 2021bnw with TARDIS to inspect the chemical composition at late photospheric phases and identify helium features. We also use a STELLA model coupling hydrodynamics and radiation transport to constrain the physical parameters of the explosion assmunig a 56Ni+CSM scenario. Results. We suggest that SN 2021bnw was mainly powered by the interaction of the ejecta with a previously lost He-rich circumstellar material, coupled with a central power source. Conclusions. This work expands the data sample of He-rich superluminous supernovae rich (SLSNe Ib) and, assuming a single progenitor scenario, can constrain the masses and the physics of their progenitors.