Relativistic axions from collapsing Bose stars

TL;DR

This paper investigates the universal collapse behavior of Bose stars made of axion-like particles, revealing a self-similar infall process and relativistic particle emission that influence dark matter substructure evolution.

Contribution

It uncovers a novel universal collapse mechanism in Bose stars driven by self-interaction, involving wave collapse and relativistic particle outflows, with implications for dark matter physics.

Findings

Collapse proceeds via self-similar wave collapse.

Dense centers emit relativistic particles.

Collapse halts when the star can no longer sustain infall.

Abstract

The substructures of light bosonic (axion-like) dark matter may condense into compact Bose stars. We study collapses of the critical-mass stars caused by attractive self-interaction of the axion-like particles and find that these processes proceed in an unexpected universal way. First, nonlinear self-similar evolution (called "wave collapse" in condensed matter physics) forces the particles to fall into the star center. Second, interactions in the dense center create an outgoing stream of mildly relativistic particles which carries away an essential part of the star mass. The collapse stops when the star remnant is no longer able to support the self-similar infall feeding the collisions. We shortly discuss possible astrophysical and cosmological implications of these phenomena.