Saturn-mass planet M dwarf GL649

Jovian Number of posts : 564 Registration date : 2008-11-12

Quote :: We report precise Doppler measurements of the nearby (d = 10.34 pc) M dwarf Gl649 that reveal the presence of a planet with a minimum mass Msini = 0.328 Mjup in an eccentric (e = 0.30), 598.3 day orbit. Our photometric monitoring reveals Gl649 to be a new variable star with brightness changes on both rotational and decadal timescales. However, neither of these timescales are consistent with the 600-day Doppler signal and so provide strong support for planetary reflex motion as the best interpretation of the observed radial velocity variations. Gl649b is only the seventh Doppler-detected giant planet around an M dwarf. The properties of the planet and host-star therefore contribute significant information to our knowledge of planet formation around low-mass stars. We revise and refine the occurrence rate of giant planets around M dwarfs based on the California Planet Survey sample of low-mass stars (M* < 0.6 Msun). We find that f = 3.4^{+2.2}_{-0.9}% of stars with M* < 0.6 Msun harbor planets with Msini > 0.3$ Mjup and a < 2.5 AU. When we restrict our analysis to metal-rich stars with [Fe/H] > +0.2 we find the occurrence rate is 10.7^{+5.9}_{-4.2}%.

Jovian Number of posts : 564 Registration date : 2008-11-12

Quote :: Note that in the analysis that follows, we exclude the recently detected planets Gl 832 b, which was discovered by the Anglo-Australian Observatory planet search (Bailey et al. 2008), and HIP 79431b, which was only recently added to the Keck survey as part of the metallicity-biased M-to-K program (Apps et al. 2010, submitted).

HIP 79431
M3.5 star
0.5 mass Sun
[Fe/H] +0.4
sin i (MJup) 1.1
Semimajor Axis (AU) 0.34
Apps et al. (2010, submitted)