The California Planet Survey II. A Saturn-Mass Planet Orbiting the M Dwarf Gl649

John Asher Johnson; Andrew W. Howard; Geoffrey W. Marcy; Brendan P. Bowler; Gregory W. Henry; Debra A. Fischer; Kevin Apps; Howard Isaacson; Jason T. Wright

doi:10.1086/651007

arXiv · 0912.2730

The California Planet Survey II. A Saturn-Mass Planet Orbiting the M Dwarf Gl649

John Asher Johnson·Andrew W. Howard·Geoffrey W. Marcy·Brendan P. Bowler·Gregory W. Henry·Debra A. Fischer·Kevin Apps·Howard Isaacson·Jason T. Wright

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Abstract

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}%.

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John Asher Johnson, Andrew W. Howard, Geoffrey W. Marcy, Brendan P. Bowler, Gregory W. Henry, Debra A. Fischer, Kevin Apps, Howard Isaacson, Jason T. Wright. 2009-12-14. The California Planet Survey II. A Saturn-Mass Planet Orbiting the M Dwarf Gl649. https://doi.org/10.1086/651007

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