VVV Survey Microlensing Events in the Galactic Center Region
  We search for microlensing events in the highly reddened areas surrounding
the Galactic center using the near-IR observations with the VISTA Variables in
the V\'ia L\'actea Survey (VVV). We report the discovery of 182 new
microlensing events, based on observations acquired between 2010 and 2015. We
present the color-magnitude diagrams of the microlensing sources for the VVV
tiles b332, b333, and b334, which were independently analyzed, and show good
qualitative agreement among themselves. We detect an excess of microlensing
events in the central tile b333 in comparison with the other two tiles,
suggesting that the microlensing optical depth keeps rising all the way to the
Galactic center. We derive the Einstein radius crossing time for all of the
observed events. The observed event timescales range from $t_E = 5$ to $200$
days. The resulting timescale distribution shows a mean timescale of
$<t_E>=30.91$ days for the complete sample ($N = 182$ events), and
$<t_E>=29.93$ days if restricted only for the red clump (RC) giant sources ($N
= 96$ RC events). There are 20 long timescale events ($t_E \geq 100$ days) that
suggest the presence of massive lenses (black holes) or disk-disk event. This
work demonstrates that the VVV Survey is a powerful tool to detect
intermediate/long timescale microlensing events in highly reddened areas, and
it enables a number of future applications, from analyzing individual events to
computing the statistics for the inner Galactic mass and kinematic
distributions, in aid of future ground- and space-based experiments.
