A&A 535, A54 (2011) Astronomy DOI: 10.1051/0004-6361/200913580 & c ESO 2011 Astrophysics The HARPS search for southern extra-solar planets XXIX. Four new planets in orbit around the moderatly active dwarfs HD 63765, HD 104067, HD 125595, and HIP 70849, D. Ségransan1, M. Mayor1,S.Udry1,C.Lovis1,W.Benz2, F. Bouchy3,4,G.LoCurto7, C. Mordasini2,5, C. Moutou6, D. Naef1,F.Pepe1,D.Queloz1, and N. Santos8 1 Observatoire Astronomique de l’Université de Genève, 51 ch. des Maillettes – Sauverny, 1290 Versoix, Switzerland e-mail: [email protected] 2 Physikalisches Institut, Universitat Bern, Silderstrasse 5, 3012 Bern, Switzerland 3 Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre & Marie Curie, 98bis boulevard Arago, 75014 Paris, France 4 Observatoire de Haute-Provence, 04870 Saint-Michel l’Observatoire, France 5 Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany 6 Laboratoire d’Astrophysique de Marseille, UMR 6110 CNRS, Université de Provence, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France 7 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany 8 Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal Received 2 November 2009 / Accepted 29 March 2011 ABSTRACT We report the detection of four new extrasolar planets in orbit around the moderately active stars HD 63765, HD 104067, HIP 70849, and HD 125595 with the HARPS Echelle spectrograph mounted on the ESO 3.6-m telescope at La Silla. The first planet, HD 63765 b, has a minimum mass of 0.64 MJup, a period of 358 days, and an eccentricity of 0.24. It orbits a G9 dwarf at 0.94 AU. The second planet, HD 104067 b, is a 3.6 Neptune-mass-planet with a 55.8-day-period. It orbits its parent K2 dwarf, in a circular orbit with a semi-major axis of a = 0.26 AU. Radial velocity measurements present a ≈500-day-oscillation that reveals significant magnetic cycles. The third planet is a 0.77 Neptune-mass-planet in circular orbit around the K4 dwarf, HD 12595, with a 9.67-day-period. Finally, HIP 7849 b is a long-period (5 < P < 75 years) and massive planet of m sin i ≈ 3.5−15 MJup that orbits a late K7 dwarf. Key words. techniques: radial velocities – planetary systems – stars: individual: HD 63765 – stars: individual: HD 104067 – stars: individual: HD 125595 – stars: individual: HIP 70849 1. Introduction Observed distributions of planets’ orbital elements and masses, as well as host star characteristics should then be compared to The HARPS planet-search program has been going on for theoretical predictions to improve our knowledge of planet for- 6 years (since 2003) at the 3.6-m ESO telescope located at mation and evolution. La Silla Observatory, Chile (Pepe et al. 2000; Mayor et al. So far, HARPS has allowed the detection (or has contributed 2003). Both HD 63765 and HD 104067 were part of the high- to the detection) of more than 85 extrasolar planet candidates precision subprogram of the HARPS guaranted time observions (the latest batch of which was presented in a series of parallel pa- (GTO), which aimed at detecting very low-mass planets in a pers e.g. Forveille et al. 2011; Lovis et al. 2011; Mordasini et al. sample of solar-type stars already screened for giant planets at 2011; Moutou et al. 2011; Lo Curto et al. 2010; Naef et al. 2010) a lower precision with CORALIE Echelle spectrograph mounted among the ≈460 known today. But more specifically, HARPS is on the 1.2-m Swiss telescope on the same site (Udry et al. 2000). unveiling the tip of the iceberg of the very low-mass planet pop- HIP 70849 and HD 125595, on the other hand, are part of the ulation (see Lovis et al. 2009; Mayor et al. 2009), which when HARPS volume-limited sample program of the HARPS GTO. combined with forthcoming results allow extrapolating results of The sample is composed of about 1200 stars within 57.5 pc, their mass distribution. Lovis et al. (2009) show that ≈30% of the among which 850 G, K dwarfs that are known as single stars stars surveyed in the HARPS high precision program have plan- with low activity and low v sin i. The goal of this program was −1 ets with masses below 30-earth masses on periods shorter than to monitor the 850 stars at the 3 ms precision level to de- 50 days. Furthemore, ≈80% of those planets are in multplanetary tect all the gas giants present in this statistically robust sample. systems. HARPS’ high stability not only gives access to super- Earth’s at short periods but is also sensitive to Neptune-mass- The HARPS radial velocity measurements discussed in this planets at a longer period, (e.g., HD 69830 b, Lovis et al. 2006). paper are only available at the CDS via anonymous ftp to − cdsarc.u-strasbg.fr (130.79.128.5) or via The discovery of those intermediate-mass planets (1 10 MNept) http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/535/A54 in the 0.1 to 0.5 AU separation range is of interest for planetary Based on observations made with the HARPS instrument on the formation scenarios since those planets are hardly formed ac- ESO 3.6 m telescope at La Silla Observatory under the GTO pro- cording to Ida & Lin (2005) or at least, should be rare according gramme ID 072.C-0488. to Mordasini et al. (2009). Article published by EDP Sciences A54, page 1 of 8 A&A 535, A54 (2011) Table 1. Observed and inferred stellar parameters for HD 63765,HD 104067, HIP 70849 and HD 125595. Parameters HD 63765 HD 104067 HD 125595 HIP 70849 Sp. T. G9V K2V K4V K7V V 8.1 7.93 9.03 10.36 B − V 0.75 0.99 1.107 1.427 J – – – 7.639 ± 0.023 H – – – 7.006 ± 0.061 K – – – 6.790 ± 0.027 π [mas] 30.07 ± 0.56 47.47 ± 0.90 35.77 ± 1.04 42.42 ± 2.09 MV 5.49 ± 0.04 6.31 ± 0.05 6.80 ± 0.06 8.50 ± 0.10 (1) (1) (1) (4) Teff [K] 5432 ± 19 4969 ± 72 4908 ± 87 4105 ± 130 [Fe/H](1) [dex] –0.16 ± 0.01 –0.06 ± 0.05 0.02 ± 0.06 – – log (g)(1) 4.42 ± 0.03 4.47 ± 0.13 4.32 ± 0.20 – (3) (3) (3) (4) M [M] 0.865 ± 0.029 0.791 ± 0.020 0.756 ± 0.017 0.63 ± 0.03 Age [Gyr] 4.77 ± 4.07(3) 4.33 ± 3.99(3) 3.53 ± 3.59 (3) 1–5(4) ± (2) ± (2) ± (2) (5) log RHK –4.736 0.037 –4.743 0.023 –4.787 0.037 –4.697 Stellar Jitter [m/s] 3.0 3.0 2.5 3.5 v sin (i)(2) [km s−1] 1.63 1.61 1.50 1.93 Prot [days] 23 34.7 40.1 – Notes. Near infrared photometry is taken from the 2MASS All-Sky Catalog, (Cutri et al. 2003; Skrutskie et al. 2006). Astrometric data and visual photometry come from from Hipparcos Catalogs, (ESA 1997; van Leeuwen 2007). Other parameters come from: (1) Sousa et al. (2008) spectroscopic analysis; (2) HARPS CCF; (3) Girardi et al. (2000) models; (4) Baraffeetal.(1998) models; (5) Gray et al. (2006). In this paper we report the detection of four planets orbit- Table 2. Number of measurement, time span, and weighted rms ing moderately active stars. Two of them are Neptunian planets of the residuals around the one planet solutions for HD 63765 for at relatively short periods orbiting HD 104067 and HD 125595. CORALIE-98, CORALIE-07, and HARPS. The other two are gas giants at longer periods in orbit around HD 63765 and HIP 70849. The paper is organized as follows. Instrument Nmes Span σ(O−C) In the first section we briefly discuss the primary-star proper- [years] [ms−1] ties. Data analysis is presented in Sect. 3.1 while radial-velocity CORALIE-98 38 7.0 9.6 measurements and orbital solutions are discussed in Sect. 3.In CORALIE-07 18 3.18 4.72 Sect. 4, we provide concluding remarks. HARPS 52 6.3 3.27 2. Stellar characteristics accurate mass-luminosity relations (Baraffe et al. 1998; Delfosse ff The e ective temperatures, gravity, and metallicities were de- et al. 2000), to derive its fundamental physical parameters. The rived from the spectroscopic analysis of the HARPS targets list of all stellar parameters can be found in Table 1. as described in Sousa et al. (2008). We used the improved R Hipparcos astrometric parallaxes rederived by van Leeuwen The four stars have activity indexes, log HK , ranging be- (2007) to determine the absolute V-band magnitude using tween −4.69 and −4.80, and they show a large Ca II re-emission the apparent visual magnitude from Hipparcos (ESA 1997). at λ = 3933.66 Å (see Fig. 1), revealing significant chromo- Metallicities, together with the effective temperatures and MV spheric activity possibly induced by stellar spots or plagues. ff were then used to estimate basic stellar parameters (ages, In addition, log RHK indexes display variability on di erent masses) bases on theoretical isochrones from Girardi et al. time-scales as observed on their periodograms (see Fig. 1). Short (2000) and a Bayesian estimation method described in da Silva time-scale variation can often be matched to the rotation pe- 1 et al.