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We report the observation of the first gravitational microlensing event in a sparse stellar field, involving the brightest (V=11.4 mag) andclosest (~ 1 kpc) source star to date. This event was discovered by an amateurastronomer, A. Tago, on 2006 October 31 as a transient brightening, by ~4.5 mag during a ~15 day period, of a normal A-type star (GSC 3656-1328) in the Cassiopeia constellation. Analysis of both spectroscopic observations and the light curve indicates that this event was caused by gravitational microlensing rather than an intrinsically variable star. Discovery of this single event over a 30 year period is roughly consistent with the expected microlensing rate for the whole sky down to V = 12 mag stars. However, the probability for finding events with such a high magnification (~ 50) is much smaller, by a factor ~1/50, which implies that the true event rate may be higher than expected. This discovery indicates the potential of all sky variability surveys, employing frequent sampling by telescopes with small apertures and wide fields of view, for finding such rare transient events, and using the observations to explore galactic disk structure and search for exo-planets.
We present the first detection of parallax effects in a gravitational microlensing event. Parallax in a gravitational microlensing event observed only from the Earth appears as a distortion of the lightcurve due to the motion of the Earth around the
We report the extremely high magnification (A > 1000) binary microlensing event OGLE-2007-BLG-514. We obtained good coverage around the double peak structure in the light curve via follow-up observations from different observatories. The binary lens
We present the analysis of microlensing event MOA-2010-BLG-117, and show that the light curve can only be explained by the gravitational lensing of a binary source star system by a star with a Jupiter mass ratio planet. It was necessary to modify sta
A planetary microlensing signal is generally characterized by a short-term perturbation to the standard single lensing light curve. A subset of binary-source events can produce perturbations that mimic planetary signals, thereby introducing an ambigu
We report a measurement of the shape of the source star in microlensing event MOA 2002-BLG-33. The lens for this event was a close binary whose centre-of-mass passed almost directly in front of the source star. At this time, the source star was close