Microlensing towards the SMC: a new analysis of OGLE and EROS results
  We present a new analysis of the results of the EROS-2, OGLE-II, and OGLE-III
microlensing campaigns towards the Small Magellanic Cloud (SMC). Through a
statistical analysis we address the issue of the \emph{nature} of the reported
microlensing candidate events, whether to be attributed to lenses belonging to
known population (the SMC luminous components or the Milky Way disc, to which
we broadly refer to as "self lensing") or to the would be population of dark
matter compact halo objects (MACHOs). To this purpose, we present profiles of
the optical depth and, comparing to the observed quantities, we carry out
analyses of the events position and duration. Finally, we evaluate and study
the microlensing rate. Overall, we consider five reported microlensing events
towards the SMC (one by EROS and four by OGLE). The analysis shows that in
terms of number of events the expected self lensing signal may indeed explain
the observed rate. However, the characteristics of the events, spatial
distribution and duration (and for one event, the projected velocity) rather
suggest a non-self lensing origin for a few of them. In particular we evaluate,
through a likelihood analysis, the resulting upper limit for the halo mass
fraction in form of MACHOs given the expected self-lensing and MACHO lensing
signal. At 95% CL, the tighter upper limit, about 10%, is found for MACHO mass
of $10^{-2} \mathrm{M}_\odot$, upper limit that reduces to above 20% for $0.5
\mathrm{M}_\odot$ MACHOs.
