Multi-messenger Probes of Asteroid Mass Primordial Black Holes: Superradiance Spectroscopy, Hawking Radiation, and Microlensing

TL;DR

This paper explores how superradiance, Hawking radiation, and microlensing can jointly constrain primordial black holes as dark matter candidates in the asteroid mass range, using upcoming astronomical observations.

Contribution

It introduces a multi-messenger approach combining superradiance signals, Hawking radiation, and microlensing to probe primordial black holes as dark matter, highlighting new observational sensitivities.

Findings

Upcoming telescopes can detect signals from primordial black holes in the asteroid mass range.

Multi-messenger observations can constrain the dark matter fraction of primordial black holes.

Complementary gravitational-wave signals provide additional constraints.

Abstract

Superradiance provides a unique opportunity for investigating dark sectors as well as primordial black holes, which themselves are candidates for dark matter over a wide mass range. Using axion-like particles as an example, we show that line signals emerging from a superradiated axion cloud combined with black hole Hawking radiation in extragalactic and galactic halos, along with microlensing observations lead to complementary constraints on parameter space combinations including the axion-photon coupling, axion mass, black hole mass, and its dark matter fraction, $f_{\rm PBH}$. For the asteroid mass range $\sim10^{16}-10^{22}~{\rm g}$, where primordial black holes can provide the totality of dark matter, we demonstrate that ongoing and upcoming observations such as SXI, JWST, and AMEGO-X will be sensitive to possible line and continuum signals, respectively, providing probes of previously inaccessible regions of $f_{\rm PBH}$ parameter space. Further complementarity from a stochastic gravitational-wave background emerging from the black hole formation mechanism is also considered.