Microlensing of Kepler Stars as a Method of Detecting Primordial Black Hole Dark Matter

TL;DR

This paper proposes using Kepler's stellar data to detect primordial black hole dark matter through microlensing events, offering a new method to constrain or identify such dark matter candidates.

Contribution

It introduces a novel approach leveraging Kepler data for PBH detection and develops a new formalism for microlensing calculations with large finite-source effects.

Findings

Potential to detect PBHs in the mass range 5×10^{-10} to 10^{-4} solar masses

Non-detection could exclude nearly two orders of magnitude of PBH mass window

Enhanced microlensing rate due to Kepler's photometric precision and large stellar angular sizes

Abstract

If the Dark Matter consists of primordial black holes (PBHs), we show that gravitational lensing of stars being monitored by NASA's Kepler search for extra-solar planets can cause significant numbers of detectable microlensing events. A search through the roughly 150,000 lightcurves would result in large numbers of detectable events for PBHs in the mass range $5 \ten{-10}\msun$ to $\aten{-4}\msun$. Non-detection of these events would close almost two orders of magnitude of the mass window for PBH dark matter. The microlensing rate is higher than previously noticed due to a combination of the exceptional photometric precision of the Kepler mission and the increase in cross section due to the large angular sizes of the relatively nearby Kepler field stars. We also present a new formalism for calculating optical depth and microlensing rates in the presence of large finite-source effects.