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 m sin i > 3.8 M-J and a <= 0.7 AU. For eccentric orbits ( e 0: 6) the survey completeness is 95% for all planets with m sin i > 3.5 M-J 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.