Microlensing Constraints on the Frequency of Jupiter-Mass Companions: Analysis of Five Years of PLANET Photometry

We analyze five years of PLANET photometry of microlensing events toward the Galactic bulge to search for the short-duration deviations from single lens light curves that are indicative of the presence of planetary companions to the primary microlenses. Using strict event selection criteria, we construct a well defined sample of 43 intensively monitored events. We search for planetary perturbations in these events over a densely sampled region of parameter space spanning two decades in mass ratio and projected separation, but find no viable planetary candidates. By combining the detection efficiencies of the events, we find that, at 95% confidence, less than 25% of our primary lenses have companions with mass ratio q = 10 and separations in the lensing zone, [0.6 − 1.6]θE, where θE is the Einstein ring radius. Using a model of the mass, velocity and spatial distribution of bulge lenses, we infer that the majority of our lenses are likely M dwarfs in the Galactic bulge. We conclude that < 33% of M-dwarfs in the Galactic bulge have companions with mass mp = MJup between 1.5 and 4 AU, and < 45% have companions with mp = 3MJup between 1 and 7 AU, the first significant limits on planetary companions to M-dwarfs. We consider the effects of the finite size of the source stars and changing our detection criterion, but find that these do not alter our conclusions substantially. Subject headings: gravitational lensing, planetary systems Univ. of Canterbury, Dept. of Physics & Astronomy, Private Bag 4800, Christchurch, New Zealand Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD. 21218 U.S.A. Ohio State University, Department of Astronomy, Columbus, OH 43210, U.S.A. Institut d’Astrophysique de Paris, INSU CNRS, 98 bis Boulevard Arago, F-75014, Paris, France South African Astronomical Observatory, P.O. Box 9, Observatory 7935, South Africa Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 Hubble Fellow Univ. of Tasmania, Physics Dept., G.P.O. 252C, Hobart, Tasmania 7001, Australia Perth Observatory, Walnut Road, Bickley, Perth 6076, Australia Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands