A Planetary Companion to HD 40979 and Additional Planets Orbiting HD 12661 and HD 38529

We report the detection of three extrasolar planets from the Lick and Keck observatories. The F8 V star HD 40979 has a companion with orbital period P=263.1+/-3 days, eccentricity e=0.25+/-0.05, and velocity semiamplitude K=101.2+/-5.6 m s^-1. The inferred semimajor axis is 0.83 AU and Msini=3.28M_Jup. Observations of planetary companions orbiting the G6 V star HD 12661 and the G4 IV star HD 38529 have already been published, and here we report additional, longer period companions for both of these stars. The outer companion to HD 12661 has P_c=1444.5+/-12.5 days, e_c=0.20+/-0.04, and K_c=27.6+/-2.5 m s^-1. Adopting a stellar mass of 1.07 M_solar, we find M_csini=1.57M_Jup and a semimajor axis of 2.56 AU. The second companion to HD 38529 has P_c=2174+/-30 days, e_c=0.36+/-0.05, and K_c=170.5+/-9 m s^-1. The assumed mass of 1.39 M_solar for HD 38529 yields M_csini=12.7M_Jup and a semimajor axis of 3.68 AU. Photometric observations at Fairborn Observatory reveal low-amplitude brightness variations in HD 40979 and HD 38529 due to rotational modulation in the visibility of photospheric starspots, and they yield rotation periods of 7.0 and 35.7 days, respectively, very different from the planetary orbital periods. The orbital parameters of these two systems are compared with updated parameters for all of the known multiple-planet systems. Updated velocities are provided for the Υ Andromedae system.

Based on observations obtained at Lick Observatory, which is operated by the University of California, and the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology. Keck time has been granted by both NASA and the University of California.