On the Metal Richness of M Dwarfs with Planets

Knowledge of the metallicities of M dwarfs rests predominantly on the photometric calibration of Bonfils and collaborators, which predicts that M dwarfs in the solar neighborhood, including those with known planets, are systematically metal poor compared to their higher-mass counterparts. We test this prediction using a volume-limited sample of low-mass stars, together with a subset of M dwarfs with high-metallicity, F, G, and K wide binary companions. We find that the Bonfils et al. photometric calibration systematically underestimates the metallicities of our high-metallicity M dwarfs by an average of 0.32 dex. We derive a new photometric metallicity calibration and show that M dwarfs with planets appear to be systematically metal rich, a result that is consistent with the metallicity distribution of FGK dwarfs with planets

Planetary Companions Around Two Solar Type Stars: HD 195019 and HD 217107

We have enlarged the sample of stars in the planet search at Lick Observatory. Doppler measurements of 82 new stars observed at Lick Observatory, with additional velocities from Keck Observatory, have revealed two new planet candidates. The G3V/IV star, HD 195019, exhibits Keplerian velocity variations with a period of 18.27 d, an orbital eccentricity of 0.03 +/- 0.03, and M sin i = 3.51 M_Jup. Based on a measurement of Ca II H&K emission, this star is chromospherically inactive. We estimate the metallicity of HD 195019 to be approximately solar from ubvy photometry. The second planet candidate was detected around HD 217107, a G7V star. This star exhibits a 7.12 d Keplerian period with eccentricity 0.14 +/- 0.05 and M sin i = 1.27 M_Jup. HD 217107 is also chromospherically inactive. The photometric metallicity is found to be [Fe/H] = +0.29 +/- 0.1 dex. Given the relatively short orbital period, the absence of tidal spin-up of HD 217107 provides a theoretical constraint on the upper limit of the companion mass of < 11 M_Jup.Comment: 15 pages, plus 6 figures. To appear in Jan 1999 PAS

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

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}%.Comment: 8 pages, 4 figures, 3 tables, PASP accepte

Characterization the Cool KOIs. II. The M Dwarf KOI-254 and its Hot Jupiter

We report the confirmation and characterization of a transiting gas giant planet orbiting the M dwarf KOI-254 every 2.455239 days, which was originally discovered by the Kepler mission. We use radial velocity measurements, adaptive optics imaging, and near-infrared spectroscopy to confirm the planetary nature of the transit events. KOI-254 b is the first hot Jupiter discovered around an M-type dwarf star. We also present a new model-independent method of using broadband photometry to estimate the mass and metallicity of an M dwarf without relying on a direct distance measurement. Included in this methodology is a new photometric metallicity calibration based on J – K colors. We use this technique to measure the physical properties of KOI-254 and its planet. We measure a planet mass of M_P = 0.505 M_(Jup), radius R_P = 0.96 R_(Jup), and semimajor axis a = 0.030 AU, based on our measured stellar mass M_* = 0.59 M_☉ and radius R_* = 0.55 R_☉. We also find that the host star is metal-rich, which is consistent with the sample of M-type stars known to harbor giant planets

M2K: I. A Jovian mass planet around the M3V star HIP79431

Doppler observations from Keck Observatory reveal the presence of a planet with Msini of 2.1 Mjup orbiting the M3V star HIP79431. This is the sixth giant planet to be detected in Doppler surveys of M dwarfs and it is one of the most massive planets discovered around an M dwarf star. The planet has an orbital period of 111.7 days and an orbital eccentricity of 0.29. The host star is metal rich, with an estimated [Fe/H] = +0.4. This is the first planet to emerge from our new survey of 1600 M-to-K dwarf stars.Comment: 5 figure

HD 110067 is a wide hierarchical triple system

We report that HD 110067, the recently announced host star of a resonant sextuplet of transiting sub-Neptunes, is not a single star as claimed in the discovery paper, but a wide hierarchical triple. The K0 V planet hosting star (V = 8.4 mag, d = 32 pc) has a companion at a wide projected separation of 13400 au. This companion, namely HD 110106, is a slightly fainter (V = 8.8 mag) K3 V type 8-year period double-lined spectroscopic binary. The secondary in this spectroscopic binary is contributing a significant amount of flux and has a measured high mass ratio.Comment: Accepted for publication in RNAA

Ten Low Mass Companions from the Keck Precision Velocity Survey

Ten new low mass companions have emerged from the Keck precision Doppler velocity survey, with minimum (msini) masses ranging from 0.8 mjup to 0.34 msun. Five of these are planet candidates with msini < 12 mjup, two are brown dwarf candidates with msini ~30 mjup, and three are low mass stellar companions. Hipparcos astrometry reveals the orbital inclinations and masses for three of the (more massive) companions, and it provides upper limits to the masses for the rest. A new class of extrasolar planet is emerging, characterized by nearly circular orbits and orbital radii greater than 1 AU. The planet HD 4208b appears to be a member of this new class. The mass distribution of extrasolar planets continues to exhibit a rapid rise from 10 mjup toward the lowest detectable masses near 1 msat.Comment: 26 pages, TeX, plus 13 postscript figure

Characterizing the Cool KOIs II. The M Dwarf KOI-254 and its Hot Jupiter

We report the confirmation and characterization of a transiting gas giant planet orbiting the M dwarf KOI-254 every 2.455239 days, which was originally discovered by the Kepler mission. We use radial velocity measurements, adaptive optics imaging and near infrared spectroscopy to confirm the planetary nature of the transit events. KOI-254b is the first hot Jupiter discovered around an M-type dwarf star. We also present a new model-independent method of using broadband photometry to estimate the mass and metallicity of an M dwarf without relying on a direct distance measurement. Included in this methodology is a new photometric metallicity calibration based on J-K colors. We use this technique to measure the physical properties of KOI-254 and its planet. We measure a planet mass of Mp = 0.505 Mjup, radius Rp = 0.96 Rjup and semimajor axis a = 0.03 AU, based on our measured stellar mass Mstar = 0.59 Msun and radius Rstar = 0.55 Rsun. We also find that the host star is metal-rich, which is consistent with the sample of M-type stars known to harbor giant planets.Comment: AJ accepted (in press

M2K: I. A Jupiter-Mass Planet Orbiting the M3V Star HIP 79431

Doppler observations from Keck Observatory reveal the presence of a planet with M sin i of 2.1 M_(Jup) orbiting the M3V star HIP 79431. This is the sixth giant planet to be detected in Doppler surveys of M dwarfs and it is one of the most massive planets discovered around an M dwarf star. The planet has an orbital period of 111.7 days and an orbital eccentricity of 0.29. The host star is metal rich, with an estimated [Fe/H] = +0.4. This is the first planet to emerge from our new survey of 1600 M-to-K dwarf stars