On the Mass of the Dark Compact Objects in the Galactic Disk

Abstract

Recently the Polish-American collaboration OGLE has reported the observation of four possible microlensing events by monitoring, over several months, the brightness of millions of stars in the region of the galactic bulge. If these events are due to microlensing, the most accurate way to get information on the mass of the dark compact objects, that acted as gravitational lenses, is to use the method of the mass moments. Here I apply this method to the analysis of the events detected by OGLE. The average mass turns out to be 0.28$M_{\odot}$, suggesting that the lens objects are faint disk stars. The same method applied to the five microlensing events detected so far by the EROS and MACHO collaborations, which monitor stars in the Large Magellanic Cloud, leads to an average value of 0.08$M_{\odot}$ for the dark compact halo objects.