Geometric Search for Hawking Radiation from Nearby Primordial Black Holes

TL;DR

This paper proposes a geometric method to detect nearby primordial black holes by analyzing gamma-ray wavefronts, enabling direct distance measurements and potential insights into black hole properties.

Contribution

Introduces a novel geometric approach combining imaging and timing to measure distances to gamma-ray transients, advancing the search for primordial black holes.

Findings

Current method probes Solar-System-scale distances (~1.2 AU).

Distance measurements can reach up to 10^3 AU with existing technology.

Future detectors could extend the search to 10^5 AU and beyond.

Abstract

A nearby primordial-black-hole (PBH) evaporation burst would produce a curved gamma-ray wavefront, leading to detectable departures from plane-wave inter-satellite delays. We introduce a purely geometric method that combines imaging localizations with multi-spacecraft timing to determine the distance of a gamma-ray transient. Applied to \textit{Swift}-localized short GRBs, the current sample shows no significant deviation from the plane-wave expectation, with the most constraining event reaching $1.2$ AU and already probing a meaningful Solar-System-scale regime. Our analysis shows that direct distance measurements are achievable to $10^3$ AU scales with the current and near-future technical capabilities. Once a finite source distance is measured, the corresponding PBH mass and lifetime can be directly inferred. Future wide-field localization and long-baseline deep-space gamma-ray detectors could extend such searches to $10^5$ AU and beyond.