The pair-instability origin of supernova 2023vbw

TL;DR

This paper presents detailed observations and modeling of supernova 2023vbw, a luminous, long-duration event consistent with pair-instability supernova predictions, revealing insights into the deaths of the most massive stars.

Contribution

It provides the first comprehensive observational evidence linking a supernova to the pair-instability explosion mechanism in a low-metallicity environment.

Findings

Supernova 2023vbw had a luminous, long-duration peak with a total radiated energy of 3×10^{50} erg.

Progenitor estimated to be a blue supergiant with 170-350 M$_\odot$ and explosion energy of (6-13)×10^{52} erg.

Spectra and light curves indicate interaction with an aspherical circumstellar medium.

Abstract

Stars in the initial and carbon-oxygen core mass ranges of $\sim140-260$ and $50-130$ M$_\odot$, respectively, with low metallicity are predicted to experience copious electron-positron pair production in their cores, leading to a runaway thermonuclear explosion that obliterates the entire star in a luminous and long-duration pair-instability supernova explosion. Some previous supernovae have been interpreted in this context but lack the full range of predicted properties. Here, we report detailed observations and modeling of the hydrogen-rich supernova 2023vbw, which exploded in a low-metallicity ($\sim0.1$ Z$_\odot$) environment in a dwarf star-forming galaxy at a redshift of $0.088$. Its light curve exhibits a luminous ($1.6\times10^{43}$ erg s$^{-1}$) and long-duration ($190$ days) main peak, resulting in a total radiated energy of $3\times10^{50}$ erg, more than an order of magnitude greater than canonical core-collapse supernovae. Semi-analytical light-curve modeling yields a blue supergiant-like progenitor with an ejecta mass of $170-350$ M$_\odot$, radioactive nickel mass of $1.2-1.6$ M$_\odot$, and explosion energy of $(6-13)\times10^{52}$ erg, well matched by pair-instability models. The early and late-phase light curve and spectra also show evidence for interaction of the supernova ejecta with an aspherical circumstellar medium. Discoveries of numerous such events with the upcoming Rubin Observatory and Roman Space Telescope will shed light on the deaths of the most massive stars in the Universe.