A very faint core-collapse supernova in M85

TL;DR

This paper discusses a very faint, long-lasting transient in galaxy M85, proposing it as possibly the faintest supernova ever observed, with implications for understanding low-luminosity stellar explosions.

Contribution

It presents evidence supporting the interpretation of the transient as an extremely low-luminosity type II-plateau supernova, expanding knowledge of supernova diversity.

Findings

Transient had very low luminosity and long duration.

Spectral lines and color suggest supernova origin.

Potentially the faintest supernova observed to date.

Abstract

An anomalous transient in the early Hubble-type (S0) galaxy Messier 85 (M85) in the Virgo cluster was discovered by Kulkarni et al. (2007) on 7 January 2006 that had very low luminosity (peak absolute R-band magnitude MR of about -12) that was constant over more than 80 days, red colour and narrow spectral lines, which seem inconsistent with those observed in any known class of transient events. Kulkarni et al. (2007) suggest an exotic stellar merger as the possible origin. An alternative explanation is that the transient in M85 was a type II-plateau supernova of extremely low luminosity, exploding in a lenticular galaxy with residual star-forming activity. This intriguing transient might be the faintest supernova that has ever been discovered.