Exploring the frequency of close-in Jovian planets around M dwarfs

We discuss our high-precision radial velocity results of a sample of 90 M dwarfs observed with the Hobby-Eberly Telescope and the Harlan J. Smith 2.7 m Telescope at McDonald Observatory, as well as the ESO VLT and the Keck I telescopes, within the context of the overall frequency of Jupiter-mass planetary companions to main-sequence stars. None of the stars in our sample show variability indicative of a giant planet in a short-period orbit, with a<=1 AU. We estimate an upper limit of the frequency f of close-in Jovian planets around M dwarfs as <1.27% (at the 1 sigma confidence level). Furthermore, we determine that the efficiency of our survey in noticing planets in circular orbits is 98% for companions with msini>3.8MJ and a<=0.7 AU. For eccentric orbits (e=0.6) the survey completeness is 95% for all planets with msini>3.5MJ and a<=0.7 AU. Our results point toward a generally lower frequency of close-in Jovian planets for M dwarfs as compared to FGK-type stars. This is an important piece of information for our understanding of the process of planet formation as a function of stellar mass. Based on data collected with the Hobby-Eberly Telescope, which is operated by McDonald Observatory on behalf of the University of Texas at Austin, Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen. Also based on observations collected at the European Southern Observatory, Chile (ESO programs 65.L-0428, 66.C-0446, 267.C-5700, 68.C-0415, 69.C-0722, 70.C-0044, 71.C-0498, 072.C-0495, 173.C-0606). Additional data were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration (NASA), and with the McDonald Observatory Harlan J. Smith 2.7 m telescope