On the mass of the dark compact objects in the Galactic disk

Recently the Polish-American collaboration OGLE has reported the observationof four possible microlensing events by monitoring, over several months, thebrightness of millions of stars in the region of the galactic bulge. If theseevents are due to microlensing, the most accurate way to get information on themass of the dark compact objects, that acted as gravitational lenses, is to usethe method of the mass moments. Here I apply this method to the analysis of theevents 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 appliedto the five microlensing events detected so far by the EROS and MACHOcollaborations, which monitor stars in the Large Magellanic Cloud, leads to anaverage value of 0.08$M_{\odot}$ for the dark compact halo objects.Comment: 8 pages, latex, CERN-TH.7191/94 and Zurich University ZU-TH 8/9