Using the Supernova / Acceleration Probe (SNAP) to Search for Microlensing Events Towards the LMC

Microlensing experiments today have a tantalizing result; they have detected an excess of microlensing events beyond what is expected from known stellar populations. These events could be due to a possible form of Halo dark matter. However, study of these events is limited by their small number and poor photometric precision. The SNAP satellite, which has been proposed to search for supernovae, would be an ideal instrument to search for microlensing events towards the LMC. Due in part to its larger mirror, and largely to its superb space-based seeing and low background, with a modest program SNAP will be able to detect ∼ 250 microlensing events per year. In addition, SNAP will generate ∼ 16 high quality events per year with 1% photometric resolution. These data should break the microlensing degeneracy, and determine whether the events are indeed due to dark matter lenses in the Galactic Halo. Side benefits of such a program will include a never before equaled catalog of variable stars in the LMC. On of the most intriguing possibilities is a direct measurement of the distance to the LMC. Such a measurement will determine what is today the most uncertain rung on the distance ladder and thus lock down the Hubble constant. Subject headings: Dark matter — Gravitational lensing