The HARPS search for southern extra-solar planets. IX. Exoplanets orbiting HD 100777, HD 190647, and HD 221287

Context: The HARPS high-resolution high-accuracy spectrograph was made available to the astronomical community in the second half of 2003. Since then, we have been using this instrument for monitoring radial velocities of a large sample of Solar-type stars (≃1400 stars) in order to search for their possible low-mass companions.
Aims: Amongst the goals of our survey, one is to significantly increase the number of detected extra-solar planets in a volume-limited sample to improve our knowledge of their orbital elements distributions and thus obtain better constraints for planet-formation models.
Methods: Radial-velocities were obtained from high-resolution HARPS spectra via the cross-correlation method. We then searched for Keplerian signals in the obtained radial-velocity data sets. Finally, companions orbiting our sample stars were characterised using the fitted orbital parameters.
Results: In this paper, we present the HARPS radial-velocity data and orbital solutions for 3 Solar-type stars: HD 100777, HD 190647, and HD 221287. The radial-velocity data of HD 100777 is best explained by the presence of a 1.16 M_Jup planetary companion on a 384-day eccentric orbit (e = 0.36). The orbital fit obtained for the slightly evolved star HD 190647 reveals the presence of a long-period (P = 1038 d) 1.9 M_Jup planetary companion on a moderately eccentric orbit (e = 0.18). HD 221287 is hosting a 3.1 M_Jup planet on a 456-day orbit. The shape of this orbit is not very well-constrained because of our non-optimal temporal coverage and because of the presence of abnormally large residuals. We find clues that these large residuals result from spectral line-profile variations probably induced by processes related to stellar activity.

Based on observations made with the HARPS instrument on the ESO 3.6-m telescope at the La Silla Observatory (Chile) under the GTO programme ID 072.C-0488. Tables 2-4 are only available in electronic form at http://www.aanda.org