Short-duration lensing events: II. Expectations and Protocols

Abstract

Ongoing microlensing observations by OGLE and MOA regularly identify and conduct high-cadence sampling of lensing events with Einstein diameter crossing time, tau_E, of 16 or fewer days. Events with estimated values of tau_E of one to two days have been detected. Short duration events tend to be generated by low-mass lenses or by lenses with high transverse velocities. We compute the expected rates, demonstrate the expected ranges of parameters for lenses of different mass, and develop a protocol for observing and modeling short-duration events. Relatively minor additions to the procedures presently used will increase the rate of planet discovery, and also discover or place limits on the population of high-speed dim stars and stellar remnants in the vicinity of the Sun.Comment: 17 pages; 3 figures; submitted to ApJ 3 July 200