Astronomy and Astrophysics – Astronomy
Scientific paper
May 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998apj...498l.153s&link_type=abstract
Astrophysical Journal Letters v.498, p.L153
Astronomy and Astrophysics
Astronomy
168
Stars: Planetary Systems, Stars: Activity, Convection, Stars: Spots, Stars: Late-Type, Techniques: Radial Velocities
Scientific paper
The discovery of the radial velocity ( vr ) signatures of planets around several solar-like stars highlights the importance of exploring the sources of vr variations intrinsic to the stars themselves. We study the stars in the Lick planetary survey for vr variations related to stellar activity: the rotation of starspots and convective inhomogeneities and their temporal evolution. We study the relationships between the weighted vr dispersion, sigma ^{'}v (which has first been corrected for the orbital contribution from known planets and the mean internal error), and spectral type, rotation, and activity (as measured by Ca II H and K). We find that the largest sigma ^{'}v values occur among both the coolest (dMe) and the warmest (active F) stars. Values of sigma ^{'}v increase with H and K emission and scale proportional to v{sin}i in G and K stars and proportional to (v{sin}i)^{1.3} in F stars. For a G star with v{sin}i ~ 8-10 km s ^{-1} (age ~0.3 Gyr), for example, 20 {m} {s}^{-1}<~ sigma ^{'}v<~45 {m} {s}^{-1} , roughly consistent with the predicted sigma ^{'}v levels due to magnetic activity (Saar & Donahue). All the stars with proposed planetary companions show sigma ^{'}v values typical for their spectral type, activity, and/or rotation. However, before the planetary vr perturbations are removed, these stars show significantly enhanced sigma ^{'}v values. We develop a simple model that can predict the sigma ^{'}v expected for a given star (within ~40%) as a function of v{sin}i , spectral type, photometric variability, and macroturbulent velocity. The implications for extrasolar planet searches are discussed.
Butler Paul R.
Marcy Geoffrey W.
Saar Steven H.
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