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Disentangling stellar activity and planetary signals

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

High-precision radial-velocimetry (RV) is until now the more efficient way to discover planetary systems. Moreover, photometric transit search missions like CoRoT and Kepler, need spectroscopic RV measurements to establish the planetary nature of a transit candidate and to measure the true mass. An active star has on its photosphere dark spots and bright plages rotating with the star. These inhomogeneities of the stellar surface can induce a variation of the measurement of the RV, due to changes in lines shapes and not to a Doppler motion of the star (e.g. Queloz et al. 2001; Desort et al. 2007; Boisse et al. 2009). We study how the Keplerian fit used to search for planets in RV data is confused by spots and we test an approach to subtract RV jitter based on harmonic decomposition of the star rotation. We use simulations of spectroscopic measurements of rotating spotted stars and validate our approach on active stars monitored by high-precision spectrograph HARPS: CoRoT-7 and ι Hor.

techniques: radial velocities, planetary systems, stars: activity, stars: individual (CoRoT-7, ι Hor)

The Astrophysics of Planetary Systems: Formation, Structure, and Dynamical Evolution
Proceedings IAU Symposium No. 276

A. Sozzetti, M. G. Lattanzi, A. P. Boss

Cambridge University Press
Volume 6, Page 399
2011 November

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia