A Dedicated M Dwarf Planet Search Using The Hobby-Eberly Telescope

We present first results of our planet search program using the 9.2 meterHobby-Eberly Telescope (HET) at McDonald Observatory to detect planets aroundM-type dwarf stars via high-precision radial velocity (RV) measurements.Although more than 100 extrasolar planets have been found around solar-typestars of spectral type F to K, there is only a single M-dwarf (GJ 876, Delfosseet al. 1998; Marcy et al. 1998; Marcy et al. 2001) known to harbor a planetarysystem. With the current incompleteness of Doppler surveys with respect toM-dwarfs, it is not yet possible to decide whether this is due to a fundamentaldifference in the formation history and overall frequency of planetary systemsin the low-mass regime of the Hertzsprung-Russell diagram, or simply anobservational bias. Our HET M-dwarf survey plans to survey 100 M-dwarfs in thenext 3 to 4 years with the primary goal to answer this question. Here wepresent the results from the first year of the survey which show that ourroutine RV-precision for M-dwarfs is 6 m/s. We found that GJ 864 and GJ 913 arebinary systems with yet undetermined periods, while 5 out of 39 M-dwarfs reveala high RV-scatter and represent candidates for having short-periodic planetarycompanions. For one of them, GJ 436 (rms = 20.6 m/s), we have already obtainedfollow-up observations but no periodic signal is present in the RV-data.Comment: 12 pages, 14 figures, accepted for publication in the Astronomical Journa