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We present measurements of the microlensing optical depth and event rate toward the Galactic Bulge based on two years of the MOA-II survey. This sample contains ~1000 microlensing events, with an Einstein Radius crossing time of t_E < 200 days between -5 <l< 10 degree and -7 <b< -1 degree. Our event rate and optical depth analysis uses 474 events with well defined microlensing parameters. In the central fields with |l|< 5 degree, we find an event rates of Gamma = [2.39+/-1.1]e^{[0.60pm0.05](3-|b|)}x 10^{-5}/star/yr and an optical depth of tau_{200} = [2.35+/-0.18]e^{[0.51+/-0.07](3-|b|)}x 10^{-6} for the 427 events using all sources brighter than I_s = 20 mag centered at (l,b)=(0.38, -3.72). We find that the event rate is maximized at low latitudes and a longitude of $l~1 degree. For the 111 events in 3.2 deg^2 of the central Galactic Bulge at |b| < 3.0 degree and 0.0 < l < 2.0, centered at (l,b)=(0.97, -2.26), we find Gamma = 4.57_{-0.46}^{+0.51} x 10^{-5}/star/yr and tau_{200} = 3.64_{-0.45}^{+ 0.51} x 10^{-6}. We also consider a Red Clump Giant (RCG) star sample with I_s<17.5 mag. Our results are consistent with previous optical depth measurements. We find that the previously observed difference in optical depth measurements between all-source and RCG samples may be largely due to statistical fluctuations. These event rate measurements towards the central galactic bulge are necessary to predict the microlensing event rate and to optimize the survey fields in the future space mission such as WFIRST.
We present a measurement of the microlensing optical depth toward the Galactic Bulge based on 4 years of the OGLE-II survey using Red Clump Giant (RCG). Using 32 events we find tau=2.55_{-0.46}^{+0.57}* 10^{-6} at (l,b)=(1.16, -2.75). Taking into acc
Searches for gravitational microlensing events are traditionally concentrated on the central regions of the Galactic bulge but many microlensing events are expected to occur in the Galactic plane, far from the Galactic Center. Owing to the difficulty
We analyze the data of the gravitational microlensing survey carried out by by the MOA group during 2000 towards the Galactic Bulge (GB). Our observations are designed to detect efficiently high magnification events with faint source stars and short
We present a new EROS-2 measurement of the microlensing optical depth toward the Galactic Bulge. Light curves of $5.6times 10^{6}$ clump-giant stars distributed over $66 deg^2$ of the Bulge were monitored during seven Bulge seasons. 120 events were f
We find that significant incompleteness in stellar number counts results in a significant overestimate of the microlensing optical depth $tau$ and event rate per star per year $Gamma$ toward the Galactic bulge from the first two years of the MOA-II s