Improved Theoretical Predictions of Microlensing Rates for the Detection of Primordial Black Hole Dark Matter

TL;DR

This paper refines the theoretical predictions for microlensing detection of primordial black hole dark matter, extending the detectable mass range and improving modeling accuracy for future surveys.

Contribution

It introduces a more precise model for PBH microlensing detection, extending the mass range and addressing previous formula errors, with implications for future observational strategies.

Findings

Extended the detectable PBH mass range down to 2×10^{-10} M_sun.

Corrected a key finite-source limb-darkening microlensing formula.

Provided an approximation for detection rates based on star properties.

Abstract

Primordial Black Holes (PBHs) remain a Dark Matter (DM) candidate of the Standard Model of Particle Physics. Previously, we proposed a new method of constraining the remaining PBH DM mass range using microlensing of stars monitored by NASA's Kepler mission. We improve this analysis using a more accurate treatment of the population of the Kepler source stars, their variability and limb-darkening. We extend the theoretically detectable PBH DM mass range down to $2\times10^{-10} M_\sun$, two orders of magnitude below current limits and one third order of magnitude below our previous estimate. We address how to extract the DM properties such as mass and spatial distribution if PBH microlensing events were detected. We correct an error in a well-known finite-source limb-darkening microlensing formula and also examine the effects of varying the light curve cadence on PBH DM detectability. We also introduce an approximation for estimating the predicted rate of detection per star as a function of the star's properties, thus allowing for selection of source stars in future missions, and extend our analysis to planned surveys, such as WFIRST.