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 Prot of the star and its two-first harmonics Prot /2 and Prot /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: HD 189733, GJ 674, CoRoT-7 and ι Hor.
Highlights
High-precision radial-velocimetry is until now the more efficient way to discover planetary systems
Three sinusoids with periods fixed at the rotational period Prot, and its two-first harmonics Prot/2 and Prot/3 reduce the semi-amplitude of the RV jitter by more than 87%
We find for the masses 5.7±2.5 MEarth for CoRoT-7b agreeing with the value of Q09 and 13.2±4.1 MEarth, slightly higher than the published value, for CoRoT-7c
Summary
High-precision radial-velocimetry is until now the more efficient way to discover planetary systems. An active star presents on its photosphere dark spots and/or bright plages rotating with the star These inhomogeneities of the stellar surface can induce RV shifts due to changes in the spectral lines shape which may add confusion with the Doppler reflex-motion due to a planetary companion Photometric transit search missions (like CoRoT and Kepler) require RV measurements to establish the planetary nature of the transiting candidates and. These candidates include active stars adding strong confusions and difficulties in the RV follow-up
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