Search for heavy blackholes with Microlensing: The MEMO project

The historical microlensing surveys MACHO, EROS, MOA and OGLE (hereafter summarized in the MEMO acronym) have searched for microlensing toward the LMC for a total duration of 27 years. We have studied the potential of joining all databases to search for very heavy objects producing several year duration events. We show that a combined systematic search for microlensing should detect of the order of 10 events due to $100M_\odot$ black holes, that were not detectable by the individual surveys, if these objects have a major contribution to the Milky-Way halo. Assuming that a common analysis is feasible, i.e. that the difficulties due to the use of different passbands can be overcome, we show that the sensitivity of such an analysis should allow one to quantify the Galactic black hole component.