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Astron. Astrophys. 361, 265-272 (2000)

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The CORALIE survey for Southern extra-solar planets *

IV. Intrinsic stellar limitations to planet searches with radial-velocity techniques

N.C. Santos, M. Mayor, D. Naef, F. Pepe, D. Queloz, S. Udry and A. Blecha

Observatoire de Genève, 51 ch. des Maillettes, 1290 Sauverny, Switzerland

Received 6 April 2000 / Accepted 14 July 2000


Activity related phenomena can induce radial-velocity variations, which can be very important when dealing with extra-solar planet search programmes requiring high-precision radial-velocity measurements.

In this paper we present a new chromospheric activity index, [FORMULA], based on the CaII H line central reemission, and constructed using CORALIE spectra. After one year of measurements, values of [FORMULA] are available for a sub-sample of stars of the Geneva extra-solar planet search programme. After transforming the [FORMULA] values into the Mount-Wilson "S" scale we obtained values of the CaII H and K flux corrected from photospheric emission ([FORMULA]) for the stars. The first results are presented, and in particular we focus on the study of the relation between the observed radial-velocity scatter and the chromospheric activity index [FORMULA], for F, G and K dwarfs.

Key words: techniques: radial velocities – stars: planetary systems – stars: activity – stars: starspots

* Based on observations collected at the La Silla Observatory, ESO (Chile), with the echelle spectrograph coralie at the 1.2-m Euler Swiss telescope

Send offprint requests to: Nuno.Santos@obs.unige.ch

© European Southern Observatory (ESO) 2000

Online publication: September 5, 2000