Search for lensing signatures from the latest fast radio burst observations and constraints on the abundance of primordial black holes

TL;DR

This study searches for gravitational lensing signatures in fast radio burst data to constrain the abundance of primordial black holes, providing new limits especially for black holes over 500 solar masses.

Contribution

It applies a novel cross-correlation algorithm to the latest FRB data to set constraints on primordial black hole dark matter in the stellar mass range.

Findings

Constraints on PBH fraction ≤87% for ≥500 M☉ at 95% confidence.

Improved constraints by a factor of three using different flux ratio thresholds.

Current FRB constraints are weaker than gravitational wave limits for certain mass distributions.

Abstract

The possibility that primordial black holes (PBHs) form a part of dark matter has been considered for a long time but poorly constrained over a wide mass range. Fast radio bursts (FRBs) are bright radio transients with millisecond duration. Lensing effect of them has been proposed as one of the cleanest probes for constraining the presence of PBHs in the stellar mass window. In this paper, we first apply the normalised cross-correlation algorithm to search and identify candidates of lensed FRBs in the latest public FRB observations, i.e. $593$ FRBs which mainly consist of the first Canadian Hydrogen Intensity Mapping Experiment FRB catalog, and then derive constraints on the abundance of PBHs from the null search result of lensing signature. For a monochromatic mass distribution, the fraction of dark matter made up of PBHs could be constrained to $\leq87\%$ for $\geq500~M_{\odot}$ at 95\% confidence level by assuming flux ratio thresholds dependent signal-to-noise ratio for each FRB and that apparently one-off events are intrinsic single bursts. This result would be improved by a three times factor when a conventional constant flux ratio threshold is considered. Moreover, we derive constraints on PBHs with a log-normal mass function naturally predicted by some popular inflation models and often investigated with gravitational wave detections. We find that, in this mass distribution scenario, the constraint from currently public FRB observations is relatively weaker than the one from gravitational wave detections. It is foreseen that upcoming complementary multi-messenger observations will yield considerable constraints on the possibilities of PBHs in this intriguing mass window.