Astronomy and Astrophysics, volume 520, A53-53 (2010/9-2)
Photospheric activity, rotation, and radial velocity variations of the planet-hosting star CoRoT-7.
LANZA A.F., BONOMO A.S., MOUTOU C., PAGANO I., MESSINA S., LETO G., CUTISPOTO G., AIGRAIN S., ALONSO R., BARGE P., DELEUIL M., AUVERGNE M., BAGLIN A. and COLLIER CAMERON A.
Abstract (from CDS):
The CoRoT satellite has recently discovered the transits of an Earth-like planet across the disc of a late-type magnetically active star dubbed CoRoT-7, while a second planet was detected after filtering out the radial velocity (hereafter RV) variations due to stellar activity. We investigate the magnetic activity of CoRoT-7 and use the results for a better understanding of the impact of magnetic activity on stellar RV variations. We derived the longitudinal distribution of active regions on CoRoT-7 from a maximum entropy spot model of the CoRoT lightcurve. Assuming that each active region consists of dark spots and bright faculae in a fixed proportion, we synthesized the expected RV variations. Active regions are mainly located at three active longitudes that appear to migrate at different rates, probably as a consequence of surface differential rotation, for which a lower limit of ΔΩ/Ω=0.058±0.017 is found. The synthesized activity-induced RV variations reproduce the amplitude of the observed RV curve and are used to study the impact of stellar activity on planetary detection. In spite of the non-simultaneous CoRoT and HARPS observations, our study confirms the validity of the method previously adopted to filter out RV variations induced by stellar activity. We find a false-alarm probability <10–4 that the RV oscillations attributed to CoRoT-7b and CoRoT-7c are spurious effects of noise and activity. Additionally, our model suggests that other periodicities found in the observed RV curve of CoRoT-7 could be explained by active regions whose visibility is modulated by a differential stellar rotation with periods ranging from 23.6 to 27.6 days.
stars: activity - stars: magnetic field - stars: late-type - stars: rotation - planetary systems - stars: individual: CoRoT-7
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