Planetary transits toward the Galactic bulge

One of the primary difficulties with using transits to discover extrasolar planets is the low probability a planet has of transiting its parent star. One way of overcoming this difficulty is to search for transits in dense stellar fields, such as the Galactic bulge. Here I estimate the number of planets that might be detected from a monitoring campaign toward the bulge. A campaign lasting 10 nights on a 10 m telescope (assuming 8 hr of observations per night and a 5' x 5' field of view) would detect five to 50 planets with radius R-p = 1.5 R-J or two to 15 planets with R-p = 1.0 R-J, if the frequency of planets in the bulge is similar to that in the solar neighborhood. The precise number detected depends sensitively on the distribution of planets around their parent stars. Most of those planets will be discovered around stars just below the turnoff, i.e., slightly evolved G dwarfs. Campaigns involving 1 or 4 m class telescopes are unlikely to discover any planets, unless there exists a substantial population of companions with R-p > 1.5 R-J.