Disappearance of a massive star in the Andromeda Galaxy due to formation of a black hole

TL;DR

This paper presents observational evidence of a massive star in the Andromeda Galaxy disappearing due to a failed supernova, leading to black hole formation, confirmed by multi-year optical and infrared data.

Contribution

It provides the first direct observational evidence supporting the theory that some massive stars end their lives by collapsing into black holes without a supernova explosion.

Findings

Star M31-2014-DS1 faded by over 10,000 times in optical light.

Infrared brightening observed in 2014 prior to disappearance.

Supports the existence of failed supernovae forming black holes.

Abstract

When a massive star reaches the end of its lifetime, its core collapses and releases neutrinos that drive a shock into the outer layers (stellar envelope). A sufficiently strong shock ejects the envelope, producing a supernova. If the shock fails to eject it, the envelope is predicted to fall back onto the collapsing core, producing a stellar-mass black hole (BH) and causing the star to disappear. We report observations of M31-2014-DS1, a hydrogen-depleted supergiant in the Andromeda Galaxy. In 2014 it brightened in the mid-infrared. From 2017 to 2022 it faded by factors of $\gtrsim10^4$ in optical light, becoming undetectable, and $\gtrsim10$ in total light. We interpret these observations, and those of a previous event in NGC 6946, as evidence for failed supernovae forming stellar-mass BHs.