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| Paper: |
Further Evidence for Activity-Related Radial Velocity Variations in Cool Stars |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
1895 |
| Authors: |
Saar, S. H.; Butler, R. P.; Marcy, G. W. |
| Abstract: |
The discovery of planets around several solar-like stars by means of high precision radial velocity (vr) measurements makes it important to explore sources of vr variations intrinsic to the stars themselves. Such studies guard against false planet detections, and can guide planet searches towards stars with low vr ``noise" levels. We explore vr variations related to stellar activity - the rotation and temporal evolution of starspots and convective inhomogeneities - by studying the weighted RMS of vr variations (= sigma_v) for stars in the Lick planetary survey. After removing vr effects of known planets and binaries, and correcting sigma_v for the mean internal error (thus removing measurement RMS to first order), we study relationships between sigma_v and spectral type, rotation, and activity. Excluding binaries and evolved stars in the sample, we find sigma_v decreases with decreasing Teff, increases with activity level, and scales propto v sin i. For a G star with v sin i ~8-10 km s^{-1} (age ~0.3 Gyr), for example, sigma_v ~20-45 m s^{-1}, roughly consistent with the predictions of Saar & Donahue (1997). Implications for planet searches are discussed. |
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