The Black Hole Mass Gap as a New Probe of Millicharged Particles

TL;DR

This paper explores how millicharged particles could influence black hole formation, suggesting gravitational wave data can set new constraints on these particles within specific mass and charge ranges.

Contribution

It introduces a novel astrophysical method to constrain millicharged particles using the black hole mass gap affected by pulsational pair-instability supernovae.

Findings

MCP emission affects stellar pulsations and mass retention.

The lower edge of the black hole mass gap shifts with MCP properties.

Gravitational wave observations can constrain MCP parameter space.

Abstract

We investigate the impact of millicharged particles (MCPs) on massive stars undergoing pulsational pair-instability supernovae and on the location of the lower edge of the black hole mass gap. We find that energy losses due to MCP emission weaken the pulsations, allowing the star to retain more mass and thereby shifting the lower edge of the mass gap to higher black hole masses. The mass gap is sensitive to a region of MCP parameter space with masses $35\,{\rm keV}\lesssim m_\chi \lesssim 200\,{\rm keV}$ and charges $10^{-10}\lesssim q \lesssim 10^{-9}$, which remains unconstrained by existing astrophysical probes. If confirmed, recent gravitational wave observations placing the lower edge of the mass gap near $45\,{\rm M}_\odot$ would translate directly into bounds on this parameter space.