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Disentangling between stellar activity and planetary signals

  • Isabelle Boisse (a1) (a2), François Bouchy (a1) (a3), Guillaume Hébrard (a1) (a3), Xavier Bonfils (a4) (a5), Nuno Santos (a2) and Sylvie Vauclair (a6)...
Abstract
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 deeper understanding and characterization of the effects of stellar activities 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. We succeed in fitting simultaneously activity and planetary signals on GJ674 and CoRoT-7. We excluded short-period low-mass exoplanets around ι Hor. Our approach is efficient to disentangle reflex-motion due to a planetary companion and stellar-activity induced-RV variations provided that 1) the planetary orbital period is not close to that of the stellar rotation or one of its two-first harmonics, 2) the rotational period of the star is accurately known, 3) the data cover more than one stellar rotational period.

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This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

I. Boisse , C. Moutou , & A. Vidal-Madjar 2009, A&A, 495, 959

X. Bonfils , M. Mayor , & X. Delfosse 2007, A&A, 474, 293

M. Desort , A.-M. Lagrange , & F. Galland 2007, A&A, 473, 983

N. Huélamo , P. Figueira , & X. Bonfils 2008, A&A (Letters), 489, L9

A. Léger , D. Rouan , & J. Schneider 2009, A&A (Letters), 506, 287

D. Queloz , G. W. Henry , & J. P. Sivan 2001, A&A, 379, 279

D. Queloz , F. Bouchy , C. Moutou , A. Hatzes , & G. Hébrard 2009, A&A, 506, 303

S. H. Saar & R. Donahue 1997, ApJ, 485, 319

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Proceedings of the International Astronomical Union
  • ISSN: 1743-9213
  • EISSN: 1743-9221
  • URL: /core/journals/proceedings-of-the-international-astronomical-union
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