Ultrahigh-energy Gamma Rays and Gravitational Waves from Primordial Exotic Stellar Bubbles

TL;DR

This paper introduces a new class of primordial exotic stellar bubbles containing primordial black holes, which can produce detectable ultrahigh-energy gamma rays and gravitational waves, linking early universe phase transitions to observable signals.

Contribution

It proposes a novel type of primordial stellar bubbles with black holes that explain gamma-ray observations and predict gravitational wave signals for future detection.

Findings

Bubbles can fit LHAASO gamma-ray data.

Predicted GW signals are testable by upcoming surveys.

Black hole processes inside bubbles produce observable emissions.

Abstract

We put forward a novel class of exotic celestial objects that can be produced through phase transitions occurred in the primordial Universe. These objects appear as bubbles of stellar sizes and can be dominated by primordial black holes (PBHs). We report that, due to the processes of Hawking radiation and binary evolution of PBHs inside these stellar bubbles, both electromagnetic and gravitational radiations can be emitted that are featured on the gamma-ray spectra and stochastic gravitational waves (GWs). Our results reveal that, depending on the mass distribution, the exotic stellar bubbles consisting of PBHs provide not only a decent fit for the ultrahigh-energy gamma-ray spectrum reported by the recent LHAASO experiment, but also predict GW signals that are expected to be tested by the forthcoming GW surveys.