Ten Low-Mass Companions from the Keck Precision Velocity Survey

Ten new companions have emerged from the Keck precision Doppler velocity survey, with minimum (Msini) masses ranging from 0.8 M_JUP to 0.34 M_solar. Five of these are planet candidates with Msini<12 M_JUP, two are brown dwarf candidates with Msini~30 M_JUP, 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 M_JUP toward the lowest detectable masses near 1 M_SAT. Based on observations obtained at Lick Observatory, which is operated by the University of California, and on observations obtained at 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.