Saar, Steven H.

Contact Email: saar@cfa.harvard.edu
Institute: Smithsonian Astrophysical Observatory
First Coauthor: Artie iP. Hatzes
Institute: Tautenberg Obs., Germany
Second Coauthor: William D. Cochran
Institute: University of Texas, Austin
Subject Area: Brown Dwarfs & Extrasolar Planets
Waveband: Optical
Technique: Spectroscopy
Presentation: Poster Display
Title: Stellar Intrinsic Radial Velocity Noise: Properties and Possible Cures
Abstract: Study of $\sim$5 years of Lick planet survey radial velocities (v_r) shows correlations between the rms v_r dispersion, $\sigma_{v_r}$, and $v\sin i$, $P_{\rm rot}$, and $R'_{\rm HK}$. The relations are similar to those of Saar et al. (1998) but with larger scatter - probably due to a larger contribution of magnetic cycle-induced v_r variations in the new, longer timeseries. $\sigma_{v_r}$ from the Texas Hyades planet survey agree with the Lick relations, and emphasize that even in relatively young ($\sim$0.6 Gyr) stars, the $\sigma_{v_r}$ minimum in the mid-to-late K dwarfs makes them attractive targets for planet searches. The $\sigma_{v_r}$ for $\approx$22% of the Lick sample (mostly the less active stars) can be improved by an average of $\sim$50% by removing v_r-Ca II IR correlations. These corrections may prove useful in correcting v_r variations due to long term activity changes. We also present some preliminary correlations between line bisector and v_r variations which should be useful (once fully understood) in correcting short term v_r perturbations due to activity.