2001ApJ...552..731S

We present the photometry and theoretical models for a Galactic bulge microlensing event, OGLE-2000-BUL-43. The event is very bright, with I=13.54 mag, and has a very long timescale, t_E=156 days. The long timescale and its light curve deviation from the standard shape strongly suggest that it may be affected by the parallax effect. We show that OGLE-2000-BUL-43 is the first discovered microlensing event, in which the parallax distortion is observed over a period of 2 yr. Difference image analysis (DIA) using the PSF matching algorithm of Alard & Lupton enabled photometry accurate to 0.5%. All photometry obtained with DIA is available electronically. Our analysis indicates that the viewing condition from a location near Jupiter will be optimal and could lead to magnifications of ∼50 around 2001 January 31. These features offer a great promise for resolving the source (a K giant) and breaking the degeneracy between the lens parameters, including the mass of the lens, if the event is observed with the imaging camera on the Cassini space probe.