Disentangling stellar activity and planetary signals

I. Boisse, F. Bouchy, G. Hébrard, X. Bonfils, N. C. Santos, S. Vauclair

Abstract
Photospheric stellar activity (i.e. dark spots or bright plages) might be an important source of noise and confusion in the radial-velocity (RV) measurements. Radial-velocimetry planet search surveys as well as follow-up of photometric transit surveys require a deep understanding and precise characterization of the effects of stellar activity, in order to disentangle it from planetary signals.
We simulate dark spots on a rotating stellar photosphere. The variations of the RV are characterized and analyzed according to the stellar inclination, the latitude and the number of spots. The Lomb-Scargle periodograms of the RV variations induced by activity present power at the rotational period P_rot of the star and its two-first harmonics P_rot/2 and P_rot/3. Three adjusted sinusoids fixed at the fundamental period and its two-first harmonics allow to remove about 90% of the RV jitter amplitude. We apply and validate our approach on four known active planet-host stars: HD189733, GJ 674, CoRoT-7 and ɩHor.

EPJ Web of Conferences
(Eds.) F. Bouchy, R. Díaz, C. Moutou

EDP Sciences
Vol. 11, Page 02005_1
2011

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