A Multi-Wavelength Survey of Transient Lensing Opportunities for Primordial Black Hole Searches

TL;DR

This paper systematically evaluates the potential of multi-wavelength transient lensing searches across over twenty decades in photon frequency and twelve orders of magnitude in PBH mass, providing a comprehensive roadmap for future primordial black hole detection efforts.

Contribution

It offers the first broad, multi-wavelength assessment of transient lensing opportunities for PBH searches, including physical reach, observational requirements, and a unified mass-abundance framework.

Findings

Identifies accessible PBH mass windows for various transient classes.

Provides a unified mass-abundance diagram for PBH constraints.

Guides future instrument design for PBH dark matter searches.

Abstract

Gravitational lensing of short astrophysical transients provides a uniquely direct avenue for searching for primordial black holes (PBHs) across a vast range of masses. While past search efforts have focused on particular source classes-such as fast radio bursts (FRBs) and gamma-ray burst spikes-no systematic, multi-wavelength assessment has compared their relative potential for PBH discovery. We present here a broad assessment of transient lensing search opportunities, spanning more than twenty decades in photon frequency and over twelve orders of magnitude in PBH mass. For each class, we determine the accessible PBH mass window by accounting for wave-optics suppression and time-delay resolution limits, and we estimate potential sensitivities to the PBH abundance using representative event rates, distances, and optical depths. Our survey includes low-frequency radio events (FRBs, pulsar giant pulses, planetary cyclotron bursts), optical/infrared signals, and high-energy phenomena (gamma-ray burst spikes, fast X-ray transients, TeV blazar flares). We synthesize these results in a unified mass-abundance diagram and comprehensive tables summarizing both physical reach and observational requirements. This work serves as a roadmap for optimizing future multi-wavelength lensing searches, guiding the design of instruments and strategies to explore the PBH dark matter hypothesis across its remaining viable parameter space.