High Longevity Microlensing Events and Dark Matter Black Holes

Abstract

Gravitational microlensing has been employed to identify massive halo objects by their amplification of distant sources; MACHO searches have studied event times $2h\lesssim t_0\lesssim 2y$ corresponding masses in the range $10^{-6}{M}_{\odot }\lesssim M\lesssim 100M_{\odot }$. We suggest that larger masses up to $10^6{M}_{\odot }$ are also of considerable interest. It has not been excluded that there is a significant number of halo black holes with such high masses as suggested by cosmological entropy considerations and potentially detectable by high longevity microlensing events.

Comments: Table clarified