95-30619 DePoy Dr. DePoy and his Co-Principal Investigator, Dr. Andrew P. Gould, will carry out a 3-year search for extra-solar planets. The search will be based on a multi-color microlensing detection technique (see below). The instrument to be used is the Ohio State Infrared Imager and Spectrometer, which was built with previous NSF grants (AST 90-16112 to J. A. Frogel and AST 92-18449 to Dr. D. L. DePoy). Observations will be carried out at the Cerro Tololo Inter-American (CTIO) Observatory 1-meter telescope. "Microlensing" refers to the magnification of a background star when it is occulted (or nearly occulted) by a less distant star. For solar-mass stars, microlensing light curves have time scales of about two months. If the nearby star has planets, their presence can be inferred by searching for deviations from the standard microlensing light curve. Such deviations are expected to reveal themselves in less than a day. Microlensing searches require nightly photometry of millions of stars and sophisticated data processing. The investigators will rely on notification from teams that are already carrying out microlensing surveys in the attempt to detect dark matter in the universe. Dr. Depoy and his coworkers have close ties to three such microlensing/dark matter teams. Once a target has been identified, the investigators will monitor it and look for deviations from the standard microlensing light curve. Simultaneously, they will take images of the target in two widely spaced wavelengths. This additional imaging information will allow them to constrain the masses of both the star and planet, and to determine their physical separation. They estimate that they may be able to detect 10-20 Jupiter-mass planets during two years of monitoring if all stars have planetary systems similar to ours. There is a small probability of detecting planets with masses as low as the earth's. A null-result would allow the investigators to const rain the existence of planets. ***
