Abstract
We discuss the results obtained so far by microlensing towards the Andromeda galaxy. In particular, we focus on the events detected by the POINT-AGAPE and MEGA collaborations. The POINT-AGAPE collaboration concluded that at least 20% of the halo mass in the direction of
M31 should be in the form of MACHOs, whereas the MEGA collaboration, although finding more events, claimed that their result is compatible with all events being due to self-lensing. We consider the spatial and time-duration distributions of the microlensing events for several mass
distribution models of the M31 bulge. We find that only for extreme models of theM31 luminous components it is possible to reconcile the total observed MEGA events with the expected selflensing contribution. Moreover, the expected spatial distribution of self-lensing events is more
concentrated and hardly agrees with the distribution observed by the MEGA collaboration. Nevertheless, the small number of events at disposal so far does not allow to draw firm conclusions on the halo dark matter fraction in the form of MACHOs.
Jetzer, P