Superradiance in stars

TL;DR

This paper demonstrates that stars can undergo superradiant instabilities when appropriate dissipation mechanisms are present, especially due to ultra-light dark matter, leading to angular momentum loss and potential new configurations.

Contribution

It introduces the concept that stars, with suitable dissipation, are susceptible to superradiance and instabilities, extending superradiance studies beyond black holes.

Findings

Stars can experience superradiant instabilities with dissipation.

Ultra-light dark matter can trigger these instabilities.

Stars may lose most of their angular momentum over time.

Abstract

It has long been known that dissipation is a crucial ingredient in the superradiant amplification of wavepackets off rotating objects. We show that, once appropriate dissipation mechanisms are included, stars are also prone to superradiance and superradiant instabilities. In particular, ultra-light dark matter with small interaction cross section with the star material or self-annihilation can trigger a superradiant instability. On long timescales, the instability strips the star of most of its angular momentum. Whether or not new stationary configurations surrounded by scalar condensates exist, remains to be seen.