Correlating Gravitational Wave and Gamma-ray Signals from Primordial Black Holes

TL;DR

This paper explores how primordial black holes could produce detectable gamma-ray and gravitational wave signals, and how their correlation can serve as a definitive signature of their primordial origin.

Contribution

It demonstrates that gamma-ray signals from primordial black holes are detectable and correlated with a stochastic gravitational wave background, enabling precise measurement of primordial curvature fluctuations.

Findings

Gamma-ray signals from PBHs are within future detector sensitivities.

The associated GW background is detectable by planned GW observatories.

Correlation between gamma-ray and GW signals can confirm PBH origin.

Abstract

Asteroid-mass primordial black holes (PBH) can explain the observed dark matter abundance while being consistent with the current indirect detection constraints. These PBH can produce gamma-ray signals from Hawking radiation that are within the sensitivity of future measurements by the AMEGO and e-ASTROGAM experiments. PBH which give rise to such observable gamma-ray signals have a cosmic origin from large primordial curvature fluctuations. There must then be a companion, stochastic gravitational wave (GW) background produced by the same curvature fluctuations. We demonstrate that the resulting GW signals will be well within the sensitivity of future detectors such as LISA, DECIGO, BBO, and the Einstein Telescope. The multi-messenger signal from the observed gamma-rays and GW will allow a precise measurement of the primordial curvature perturbation that produces the PBH. Indeed, we argue that the resulting correlation between the two types of observations can provide a smoking-gun signal of PBH.