Electromagnetic emission from axionic boson star collisions

TL;DR

This paper investigates how collisions of axionic boson stars produce electromagnetic and gravitational signals, revealing that strong axionic couplings destabilize stars and cause electromagnetic bursts, with implications for detecting axion-like particles.

Contribution

The study provides the first nonlinear simulations of boson star dynamics with axionic couplings, demonstrating electromagnetic bursts from star decay and mergers as potential multimessenger signals.

Findings

Large axionic couplings destabilize boson stars, causing electromagnetic bursts.

Boson star mergers emit both gravitational waves and electromagnetic radiation.

Results align with flat-space estimates for critical couplings.

Abstract

We explore the dynamics of boson stars in the presence of axionic couplings through nonlinear evolutions of Einstein's field equations. We show that, for large axionic couplings, isolated boson stars become unstable, and decay via a large burst of electromagnetic radiation, becoming less massive and more dilute. Our full nonlinear results are in good agreement with flat-space estimates for the critical couplings. We then consider head-on collisions of sub-critical boson stars and study the electromagnetic and gravitational signal. Boson stars cluster around the critical point via interactions, and we argue that mergers will generically be also sources of electromagnetic radiation, in addition to gravitational waves, which can be used to place constraints on the axionic coupling if such multimessenger signals are detected.