529 Publications of the Astronomical Society of the Pacific, 114:529–535, 2002 May  2002. The Astronomical Society of the Pacific. All rights reserved. Printed in U.S.A. Planetary Companions to HD 136118, HD 50554, and HD 106252 1 Debra A. Fischer, 2 Geoffrey W. Marcy, 2 R. Paul Butler, 3 Steven S. Vogt, 4 Bernie Walp, 2 and Kevin Apps 5 Received 2002 February 2; accepted 2002 February 8; published 2002 March 25 ABSTRACT. Precise Doppler observations at Lick Observatory have revealed a substellar companion orbiting the F9 V star HD 136118 with an orbital period days, velocity semiamplitude P p 1209  24 K p 212  6 ms -1 , and eccentricity of . The assumed stellar mass of 1.24 yields a Keplerian companion 0.37  0.025 M , with and semimajor axis of 2.3 AU. We also confirm the orbital solutions for two previously M sin i p 11.9 M J announced planets, one orbiting the F8 V star HD 50554 and one orbiting the G0 V star HD 106252. Our orbital solution for HD 50554 yields days, ms -1 , and . The assumed P p 1254  34 K p 78.5  6.7 e p 0.51  0.06 stellar mass of 1.065 implies a companion mass and semimajor axis of 2.2 AU. For HD M M sin i p 3.7 M , J 106252, we find days, ms -1 , and eccentricity . The assumed P p 1503.3  62 K p 150.9  25 e p 0.57  0.11 stellar mass of 0.96 implies and semimajor axis of 2.42 AU. M M sin i p 6.96 M , J 1. INTRODUCTION High-precision Doppler techniques have detected about 80 extrasolar planets as companions to F, G, K, and M type main- sequence or subgiant stars (Butler, Marcy, & Vogt 1998; Butler et al. 1997, 1999, 2000, 2001; Butler & Marcy 1996; Cochran et al. 1997; Delfosse et al. 1998; Fischer et al. 1999, 2001, 2002; Hatzes et al. 2000; Henry et al. 2000; Jones et al. 2002; Korzennik et al. 2000; Ku ¨rster et al. 2000; Marcy & Butler 1996; Marcy, Butler, & Vogt 1999; Marcy et al. 1998, 2000, 2001a, 2001b; Mayor & Queloz 1995; Mazeh et al. 2000; Naef et al. 2001; Noyes et al. 1997; Queloz et al. 2000; Santos et al. 2001; Tinney et al. 2001, 2002; Udry et al. 2000; Vogt et al. 2000, 2002; Zucker et al. 2002). This technique is sensitive to companions that induce reflex stellar velocities, K 1 10 ms , and exhibit orbital periods ranging from a few days to -1 several years, with the maximum detectable orbital period set by the time baseline of Doppler observations. The mass distribution of known extrasolar planets rises rap- idly toward the low-mass detection threshold of the Doppler technique (Vogt et al. 2002), suggesting that lower mass objects are predominant among gas giant planets. There is essentially no observational incompleteness for companions with and orbital separations less than 3 AU. Marcy M sin i 1 10 M J & Butler (2000) estimate that less than 0.5% of ≈500 stars on 1 Based on observations obtained at Lick and Keck Observatories, which are operated by the University of California. 2 Department of Astronomy, University of California, Berkeley, CA 94720; fischer@serpens.berkeley.edu. 3 Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015-1305. 4 UCO/Lick Observatory, University of California at Santa Cruz, Santa Cruz, CA 95064. 5 Physics and Astronomy, University of Sussex, Falmer, Brighton BN1 9QJ, UK. their Keck planet search survey have substellar companions at separations less than a few AU with between 10 and M sin i 80 M J . Halbwachs et al. (2000) likewise find a minimum in the distribution of close substellar companions between 10 and 80 M J . The paucity of these companions, a so-called brown dwarf desert, apparently applies to companions at semimajor axes of tens to hundreds of AU (McCarthy 2001). At sepa- rations wider than 1000 AU, Gizis et al. (2001) suggest that brown dwarf companions may be as common as stellar com- panions in that same separation range. 2. OBSERVATIONS We are carrying out a Doppler survey of about 350 stars at Lick Observatory and about 600 stars at the Keck Observatory. The Hamilton spectrograph at Lick (Vogt 1987) has a resolution and is fed with light from either the Shane 3 m R ≈ 50,000 telescope or the 0.6 m Coude ´ auxiliary telescope (CAT). The typical signal-to-noise ratio (S/N) for stars is 140 pixel -1 V p 7 for either a single 10 minute observation with the 3 m telescope or for two 40 minute observations with the CAT telescope. The Keck project uses the HIRES spectrograph (Vogt et al. 1994) with a resolution . Exposure times for stars R ≈ 80,000 brighter than are typically 1 minute and yield S/N better V p 7 than 200. To increase phase coverage, stars showing velocity variation at Lick are often added to the Keck project. The higher S/N observations at Keck result in velocity precision that is almost uniformly a few m s -1 for chromospherically inactive stars. The Hamilton spectral format spans a wavelength range of 3700–9000 A ˚ , and the Keck spectral format spans a wavelength range of 3700–6200 A ˚ . Both projects employ an iodine cell to impose a grid of sharp reference lines between 5000 and 6000 A ˚ on the stellar spectrum. In the analysis, a high S/N template spectrum without iodine is combined with a Fourier transform