Differential Radial Velocities and Stellar Parameters of Nearby Young Stars

Radial velocity searches for substellar mass companions have focused primarily on stars older than 1 Gyr. Increased levels of stellar activity in young stars hinders the detection of solar system analogs and therefore there has been a prejudice against inclusion of young stars in radial velocity surveys until recently. Adaptive optics surveys of young stars have given us insight into the multiplicity of young stars but only for massive, distant companions. Understanding the limit of the radial velocity technique, restricted to high-mass, close-orbiting planets and brown dwarfs, we began a survey of young stars of various ages. While the number of stars needed to carry out full analysis of the problems of planetary and brown dwarf population and evolution is large, the beginning of such a sample is included here. We report on 61 young stars ranging in age from β Pic association (∼12 Myr) to the Ursa Majoris association (∼300 Myr). This initial search resulted in no stars showing evidence for companions greater than ∼1-2 MJup in short period orbits at the 3σ-level. Additionally, we present derived stellar parameters, as most have unpublished values. The chemical homogeneity of a cluster, and presumably of an association, may help to constrain true membership. As such, we present [Fe/H] abundances for the stars in our sample. Subject headings: stars: planetary systems — techniques: radial velocities — stars: activity— clusters: IC 2391, β Pic, Castor, Ursa Majoris — stars: abundances