Astronomy & Astrophysics manuscript no. harpsXXIX c ESO 2018 October 26, 2018 The HARPS search for southern extrasolar planets. XXIX. Four new planets in orbit around the moderatly active dwarfs HD 63765, HD 104067, HD 125595, and HIP 70849. ∗ y D. Segransan´ 1, M. Mayor1, S. Udry1, C. Lovis1, W- Benz2, F. Bouchy3;4, G. Lo Curto7, C. Mordasini2;5, C. Moutou6, D. Naef1, F. Pepe1, D. Queloz1, and N. Santos8 1 Observatoire Astronomique de l’Universite´ de Geneve,` 51 ch. des Maillettes - Sauverny -, CH-1290 Versoix, Switzerland 2 Physikalisches Institut, Universitat Bern, Silderstrasse 5, CH-3012 Bern, Switzerland 3 Institut d’Astrophysique de Paris, UMR 7095 CNRS, Universite´ Pierre & Marie Curie, 98bis boulevard Arago, 75014 Paris, France 4 Observatoire de Haute-Provence, 04870 Saint-Michel l’Observatoire, France 5 Max-Planck-Institut fr Astronomie, Konigstuhl¨ 17, D-69117 Heidelberg , Germany 6 Laboratoire d’Astrophysique de Marseille, UMR 6110 CNRS, Universit de Provence, 38 rue Fred´ eric´ Joliot-Curie, 13388 Marseille Cedex 13, France 7 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei Munchen¨ , Germany 8 Centro de Astrof´ısica , Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal Accepted 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 – Methods: data analysis – genetic algorithm Stars: individual: HD 63765, HD 104067, HD 125595, HIP 70849 1. Introduction present in this statistically robust sample. Observed distributions of planets’ orbital elements and masses, as well as host star char- The HARPS planet-search program has been going on for 6 acteristics should then be compared to theoretical predictions to years (since 2003) at the 3.6-m ESO telescope located at La improve our knowledge of planet formation and evolution. Silla Observatory, Chile (Pepe et al. 2000; Mayor et al. 2003). Both HD 63765 and HD 104067 were part of the high-precision So far, HARPS has allowed the detection (or has contributed subprogram of the HARPS Guaranted Time Observions (GTO), to the detection) of more than 85 extrasolar planet candidates which aimed at detecting very low-mass planets in a sample of (the latest batch of which was presented in a series of parallel pa- solar-type stars already screened for giant planets at a lower pre- pers e.g. Forveille et al. 2011; Lovis et al. 2011; Mordasini et al. cision with CORALIE Echelle spectrograph mounted on the 1.2- 2011; Moutou et al. 2011; Lo Curto et al. 2010; Naef et al. 2010) m Swiss telescope on the same site (Udry et al. 2000). HIP 70849 among the ≈460 known today. But more specifically, HARPS is and HD 125595, on the other hand, are part of the HARPS unveiling the tip of the iceberg of the very low-mass planet pop- volume-limited sample program of the HARPS GTO. The sam- ulation (see Lovis et al. 2009; Mayor et al. 2009) which when ple is composed of about 1200 stars within 57.5pc, among which combined with forthcoming results allow extrapolating results of arXiv:1107.0339v2 [astro-ph.SR] 5 Jul 2011 850 G, K dwarfs that are known as single stars with low activ- their mass distribution. Lovis et al. (2009) show that ≈30% of the ity and low v: sin i. The goal of this program was to monitor the −1 stars surveyed in the HARPS high precision program have plan- 850 stars at the 3 ms precision level to detect all the gas giants ets with masses below 30-earth masses on periods shorter than 50 days. Furthemore, ≈80% of those planets are in multplanetary Send offprint requests to: Damien Segransan,´ e-mail: HARPS [email protected] systems. ’ 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 paper are only available in electronic form at the CDS via anonymous ftp to planets at a longer period, (e.g., HD 69830 b, Lovis et al. 2006). cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi- The discovery of those intermediate-mass planets (1-10 MNept) bin/qcat?J/A+A/ in the 0.1 to 0.5 AU separation range is of interest for planetary y 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 programme cording to Ida & Lin (2005) or at least, should be rare according ID 072.C-0488. to Mordasini et al. (2009). 1 D. Segransan´ et al.: The HARPS search for southern extrasolar planets. log(R’hk) Ca II H 0.7 0.5 HD63765 0.6 0.4 0.5 0.3 0.4 0.2 0.1 Flux [Arb. Unit] 0.3 Normalized power . 0.0 . 0.2 2. 5. 10.0 20. 50. 100.0 200. 500. 1000. 2000. 5000. −3.0 −2.5 −2.0 −1.5 −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 . 0.4 . 1.2 HD104067 1.0 0.3 0.8 0.2 0.6 0.1 Flux [Arb. Unit] 0.4 Normalized power . 0.0 . 0.2 2. 5. 10.0 20. 50. 100.0 200. 500. 1000. 2000. 5000. −3.0 −2.5 −2.0 −1.5 −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 . 0.4 HD125595 1.5 0.3 1.0 0.2 0.5 0.1 Flux [Arb. Unit] Normalized power . 0.0 . 2. 5. 10.0 20. 50. 100.0 200. 500. 1000. 2000. 5000. −3.0 −2.5 −2.0 −1.5 −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 7 . 0.7 . HIP70849 6 0.6 5 0.5 0.4 4 0.3 3 0.2 2 Flux [Arb. Unit] Normalized power 0.1 1 0.0 0 2. 5. 10.0 20. 50. 100.0 200. 500. 1000. 2000. 5000. −3.0 −2.5 −2.0 −1.5 −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 . Period [days] . Wavelength − 3933.66 [Angstrom] Fig. 1. Left : Chromospheric activity index periodogram for HD 63765, HD 104067, HD 125595, and HIP 70849 . Right : Ca II H emission region. The large re-emission at the bottom of the Ca II H absorption line at λ = 3933:66 Å is an indicator of chromospheric activity. In this paper we report the detection of four planets orbit- ) of the HARPS cross-correlation function ( CCF ), as defined ing moderately active stars. Two of them are Neptunian planets by Queloz et al. (2000), as well as a measurement of the chro- 0 at relatively short periods orbiting HD 104067 and HD 125595. mospheric activity index log RHK , following a similar recipe The other two are gas giants at longer periods in orbit around as used by Santos et al. (2000) for CORALIE spectra. Using HD 63765 and HIP 70849. The paper is organized as follows. In theNoyes et al. (1984) empirical calibration of the rotational pe- the first section we briefly discuss the primary-star properties. riod vs. activity, we estimated rotational periods. We also de- Data analysis is presented in section 3.1 while radial-velocity rived the v: sin (i) from the HARPS spectra following the Santos measurements and orbital solutions are discussed in section 3. et al. (2002) approach. The HIP 70849 spectral type is, however, In section 4, we provide concluding remarks. too late (K7V) to carry out Sousa et al. (2008)’s analysis. For such a low-mass star,we have to rely on near-infrared photomet- ric measurements, as well as on accurate mass-luminosity rela- 2. Stellar characteristics tions (Baraffe et al. 1998; Delfosse et al. 2000), to derive its fun- The ffective temperatures, gravity, and metallicities were derived damental physical parameters. The list of all stellar parameters from the spectroscopic analysis of the HARPS targets as de- can be found in Table 1. scribed in Sousa et al. (2008). We used the improved Hipparcos astrometric parallaxes rederived by van Leeuwen (2007) to de- 0 termine the absolute V-band magnitude using the apparent visual The four stars have activity indexes, log RHK , ranging be- magnitude from Hipparcos (ESA 1997). Metallicities, together tween -4.69 and -4.80, and they show a large Ca II re-emission at with the effective temperatures and MV were then used to esti- λ = 3933:66 Å (see Fig.