aa r X i v : . [ a s t r o - ph ] O c t Astronomy&Astrophysicsmanuscript no. 10941 c (cid:13)
ESO 2018October 31, 2018
The HARPS search for southern extra-solar planets ⋆ XVII. Six long-period giant planets around BD -17 0063, HD 20868, HD 73267,HD 131664, HD 145377, HD 153950
C. Moutou , M. Mayor , G. Lo Curto , S. Udry , F. Bouchy , W. Benz , C. Lovis , D. Naef , F. Pepe , D. Queloz ,and N.C. Santos Laboratoire d’Astrophysique de Marseille, OAMP, Universit´e Aix-Marseille & CNRS, 38 rue Fr´ed´eric Joliot-Curie, 13388Marseille cedex 13, Francee-mail:
[email protected] Observatoire de Gen`eve, Universit´e de Gen`eve, 51 ch.des Maillettes, 1290 Sauverny, Switzerland. ESO, Alonso de Cordoba 3107, Vitacura Casilla 19001, Santiago, Chile Institut d’Astrophysique de Paris, 98bis bd Arago, 75014 Paris, France Physikalisches Institut Universit¨at Bern, Sidlerstrasse 5, 3012 Bern, Switzerland Centro de Astrof´ısica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, PortugalReceived ; accepted
ABSTRACT
We report the discovery of six new substellar companions of main-sequence stars, detected through multiple Doppler measurementswith the instrument HARPS installed on the ESO 3.6m telescope, La Silla, Chile. These extrasolar planets are orbiting the stars BD -17 0063, HD 20868, HD 73267, HD 131664, HD 145377, HD 153950. The orbital characteristics which best fit the observed data aredepicted in this paper, as well as the stellar and planetary parameters. Masses of the companions range from 2 to 18 Jupiter masses,and periods range from 100 to 2000 days. The observational data are carefully analysed for activity-induced e ff ects and we concludeon the reliability of the observed radial-velocity variations as of exoplanetary origin. Of particular interest is the very massive planet(or brown-dwarf companion) around the metal-rich HD 131664 with m sin i = Jup and a 5.34-year orbital period. These newdiscoveries reinforces the observed statistical properties of the exoplanet sample as known so far.
Key words. stars: individual: BD -17 0063, HD 20868, HD 73267, HD 131664, HD 145377, HD 153950 – stars: planetary systems– techniques: radial velocities – techniques: spectroscopic
1. Introduction
The HARPS instrument (Pepe et al. 2003; Mayor et al. 2003)has been in operation since October 2003 on the 3.6m telescopein La Silla Observatory, ESO, Chile. It has allowed so far the dis-covery of several tens of extrasolar systems, among which verylow-mass companions (e.g., Mayor et al. (2008)). The strategyof HARPS observations inside the Guaranteed Time Observationprogram is adapted to di ff erent target samples. High-precision isachieved on a sub-sample of bright stars, known to be stable at ahigh level. In addition, a larger, volume-limited sample of starsare being explored at a moderate precision (better than 3 m s − orsignal-to-noise ratio of 40) in order to complete our view of exo-planets’ properties with extended statistics. The HARPS samplecompletes the CORALIE sample with stars from 50 to 57.5 pcdistance, and together, these samples contain about 2500 stars.The results presented in this paper concern this wide exploratoryprogram at moderate precision. Earlier findings in this stellarsample consist in 8 giant planets, which have been presented inPepe et al. (2004), Moutou et al. (2005), Lo Curto et al. (2006), Send o ff print requests to : C. Moutou ⋆ Based on observations made with the HARPS instrument on theESO 3.6 m telescope at La Silla Observatory under programme ID072.C-0488(E). High-Accuracy Radial-velocity Planet Searcher and Naef et al. (2007). The statistical properties of these planetsencounter those described in the literature (Marcy et al. 2005;Udry & Santos 2007), regarding the frequency of planets and thedistribution of their parameters.We report the discovery of six new planets in the volume-limited sample of main-sequence stars, using multiple HARPSDoppler measurements over 3 to 5 years. They are massive andlong-period planets. Section 2 describes the characteristics of theparent stars, and Section 3 presents the Doppler measurementsand discusses the planetary orbital solutions.
2. Characteristics of the host stars
The host stars discussed here are: BD -17 0063, HD 20868,HD 73267, HD 131664, HD 145377, and HD 153950. We usedthe V magnitude and B − V color index given in the H ipparcos catalog (ESA 1997), and the Hipparcos parallaxes π as recentlyreviewed by van Leeuwen (2007), to estimate the absolute mag-nitude M V . The bolometric correction of Flower (1996) is thenapplied to recover the absolute luminosity of the stars.Spectroscopic parameters T e f f , log g , and [ Fe / H ] were de-rived from a set of FeI and FeII lines (Santos et al. 2004) forwhich equivalent widths were derived with ARES (AutomaticRoutine for line Equivalent width in stellar Spectra, Sousa et al.(2007, 2008)) on the HARPS spectra. The error-bars reflect the C. Moutou et al.: The HARPS search for southern extra-solar planets large number of FeI and FeII lines used, and a good precisionis obtained, especially on the e ff ective temperature. For gravityand metallicity estimates we are limited by systematics, whichare included in the error bars.We finally estimate the stellar mass and age, from T e f f ,[ Fe / H ], and parallax estimates, by using Padova models ofGirardi et al. (2000) and its web interface as described inda Silva et al. (2006). Errors are propagated and estimated usingthe Bayesian method. The stellar radius is finally estimated fromthe simple relationship between luminosity, temperature and ra-dius.From the HARPS cross-correlation function, we may derivean estimate of the projected rotational velocity of the star, v sin i .The measurement of the core reversal in the calcium H & K linesprovides an estimate of the chromospheric activity log R ′ HK (seemethod in Santos et al. (2000)). The error bars of this quantityinclude the scatter as well as some systematics; these are partic-ularly large for the faintest and coolest stars, with typical signal-to-noise ratio of 10 in the region of the calcium doublet. Allmesured stellar parameters and their errors are given in Table 1.A short presentation of the host stars follows. BD -17 0063 is a main-sequence K5 and HD 20868 is slightlyevolved K3 / M ⊙ and estimated age of more than 4 Gyr. HD 73267is somewhat more massive with 0.89 M ⊙ . It also shows no sig-nificant activity, rotates slowly and has a solar metallicity. It is a7 Gyr-old G5 dwarf. The rotation period of our sample starscan be extrapolated from the activity level using relations inNoyes et al. (1984) (colour to convection turnover time rela-tions) and Mamajek & Hillenbrand (2008) (Rossby numberto log R ′ HK relations). We find rotation periods of 39, 51 and 42days, respectively for BD -17 0063, HD 20868, and HD 73267. The other three stars HD 131664, HD 145377, and HD 153950are slightly more massive than the Sun with respecively 1.10,1.12 and 1.12 M ⊙ . HD 145377 is the most active one and itsage is estimated around 1 Gyr. Their rotational periods arealso shorter than for the first group of lower mass stars, with22, 12 and 14 days respectively for HD 131664, HD 145377,and HD 153950 . HD 131664 and HD 145377 are both metal-rich stars with [ Fe / H ] =
3. Radial velocity data and orbital solutions
We gathered 26 spectra of BD -17 0063 with HARPS over atimespan of 1760 days between October 31st 2003 and July5th 2008. The mean radial-velocity uncertainty is 1.6 m s − . Themeasurements are given in Table 3 (electronic version only) andshown in Figure 1. We fitted a Keplerian orbit to the observedradial-velocity variations, and found a best solution with a pe-riod of 655.6 days. It is an eccentric orbit ( e = .
54) with a
Fig. 1.
The radial-velocity curve of BD -17 0063 obtained withHARPS. Top: individual radial-velocity measurements (dots)versus time, and fitted orbital solution (solid curve); Middle:residuals to the fitted orbit versus time; Bottom: radial-velocitymeasurements with phase-folding, using the period of 655.6days and other orbital parameters as listed in Table 2. A 5.1 M
Jup companion to this K5 dwarf is evidenced.semi-amplitude of 173 m s − . The reduced χ obtained on thisfit is 3.2.The inverse bisector slope is estimated on the cross-correlation function and its timeseries is also examined, in orderto exclude the stellar variability as origin of the observed radial-velocity variation (Queloz et al. 2001). The error on the bisectorslope is taken as twice the error on the velocity, as a conserva-tive value. No correlation is found between the bisector slopeand the velocity, which excludes a blend scenario. The bisec-tor values for BD -17 0063 are compatible with a constant valuewith a standard deviation of 7 m s − , over the 4.8 yr time span.With the long rotation period estimated for the star (39 days),a radial-velocity modulation related to spot activity is also veryunprobable. These activity indicators thus strongly support theplanetary origin of the observed signal.With the stellar parameters as determined in the previoussection, we infer a minimum planetary mass of m sin i = . Moutou et al.: The HARPS search for southern extra-solar planets 3 Table 1.
Observed and inferred stellar parameters for the planet-hosting stars presented in this paper. a The rotation periods of thestars are not derived from observations, but indirectly inferred from log R ′ HK with relationships in Mamajek & Hillenbrand(2008) and Noyes et al. (1984). Parameter BD-17 0063 HD 20868 HD 73267 HD 131664 HD 145377 HD 153950
Sp K5V K3 / V [mag] 9.62 9.92 8.90 8.13 8.12 7.39 B − V [mag] 1.128 1.037 0.806 0.667 0.623 0.565 π [mas] 28.91 (1.27) 20.42 (1.38) 18.21 (0.93) 18.04 (0.73) 18.27 (0.94) 20.16 (0.70) d [pc] 34.6 (1.5) 48.9 (3.5) 54.91 (3.0) 55.43 (2.3) 57.7 (3.0) 49.6 (1.8) M V [mag] 6.92 6.47 5.20 4.41 4.31 3.91 B . C . [mag] -0.49 -0.41 -0.195 -0.08 -0.055 -0.038 L [ L ⊙ ] 0.21 (0.02) 0.296 (0.04) 0.783 (0.09) 1.46 (0.13) 1.56 (0.17) 2.22 (0.17) T e ff [K] 4714 (93) 4795 (124) 5317 (34) 5886 (21) 6046 (15) 6076 (13)log g [cgs] 4.26 (0.24) 4.22 (0.26) 4.28 (0.1) 4.44 (0.1) 4.49 (0.1) 4.37 (0.1)[Fe / H] [dex] -0.03 (0.06) 0.04 (0.1) 0.03 (0.02) 0.32 (0.02) 0.12 (0.01) -0.01 (0.01) M ∗ [M ⊙ ] 0.74 (0.03) 0.78 (0.03) 0.89 (0.03) 1.10 (0.03) 1.12 (0.03) 1.12 (0.03) v sin i [km s − ] 1.5 1.1 1.65 2.9 3.85 3.0log R ′ HK -4.79 (0.1) -4.99 (0.1) -4.97 (0.07) -4.82 (0.07) -4.62 (0.04) -4.89 (0.03) P rot ( HK ) a [days] 39 51 42 22 12 14Age [Gy] 4.3 (4) 4.5 (4) 7.4 (4.5) 2.4 (1.8) 1.3 (1) 4.3 (1) R ∗ [R ⊙ ] 0.69 0.79 1.04 1.16 1.14 1.34 M Jup and semi-major axis of 1.34 AU. The periastron distanceis 0.87 AU which infers a transit probability of only 0.4%. Noattempt was made yet to monitor the photometric lightcurve ofBD -17 0063 nor to search for a potential transit. Figure 1 showsthe radial-velocity signal folded with the planetary phase and theresiduals against time when the main signal is subtracted. Thereis no significant periodic trend nor linear drift in the O-C residu-als, with a standard deviation of 4.1 m s − , i.e., marginally abovethe individual errors. All parameters of the orbit and the planetare given in Table 2, together with their estimated error. Observations of HD 20868 consist in 48 HARPS measurementsobtained over 1705 days between November 1st 2003 and July2nd 2008. The mean uncertainty on the radial velocity measure-ments is 1.5 m s − . The measurements are given in Table 4 (elec-tronic version only). Figure 2 shows the velocities as a functionof time, as well as the Keplerian orbit with a period of 380.85days that best fits the data. The residual values, after subtractionof the fit, are also shown against time. There is no significanttrend in these residuals, characterized by a standard deviation of1.7 m s − . The reduced χ of the fit is 1.27.The best orbital solution is a strongly eccentric orbit ( e = − . The inferred min-imum mass of the companion responsible for this velocity vari-ation is 1.99 M Jup and a semi-major axis of 0.947 AU is derivedfrom the third Kepler law. The periastron distance is 0.54 AUwhich corresponds to a transit probability of 0.7%.The bisector test was applied and excludes that the velocityvariations are due to stellar activity. A trend which is confirmedby the long rotation period.
We gathered 39 HARPS measurements of HD 73267 over a timespan of 1586 days, from November 27th 2004 and May 31st2008. Small individual uncertainties are obtained, with a meanvalue of 1.8 m s − . Data are shown in Table 8 and in Figure 3.The observed velocity variations were fitted with a Keplerianorbit. The best solution corresponds to a period of 1260 days, eccentricity of 0.256 and semi-amplitude of 64.29 m s − . Thescatter of the residuals is compatible with the radial-velocity un-certainty and these residuals show no specific trend. The O − C standard deviation is 1.7 m s − and reduced χ is 1.19.The bisector variations are not correlated to the velocity vari-ations nor in phase with the signal, which excludes the stellarvariability as being the cause of it. Here again, the estimated ro-tation period of the star is long, and spot-related activity cannotbe considered as a potential origin for the observed signal.The minimum mass of the inferred companion is 3.06 M Jup and a semi-major axis of 2.198 AU is calculated for this 3.44year period companion.
We gathered 41 measurements of HD 131664 over 1463 dayswith HARPS, from May 21st 2004 and May 23rd 2008.Individual uncertainties have a mean value of 2 m s − . A long-term velocity variation is observed (Figure 4), which is best fit-ted with a Keplerian orbit of 1951 days, 0.638 eccentricity and alarge semi-amplitude K of 359.5 m s − . The residuals after sub-traction of this signal have a standard deviation of only 4 m s − and no specific trend. The reduced χ of the fit is 2.97. Althoughthe orbital fit to the data appears robust, the time coverageof this planetary orbit is not perfect, as most of the perias-tron passage has unfortunately been missed. This limits theprecision we get on the orbital parameters.
The bisector test again confirms the origin of this signal asdue to a sub-stellar companion. The large amplitude despite thelong period of the signal results in a large projected mass of thecompanion, i.e. m sin i = Jup . This massive planet, orbrown-dwarf companion, orbits the parent star at a semi-majoraxis of 3.17 AU.
We gathered 64 measurements of HD 145377 with HARPS fromJune 21st 2005 to July 1st 2008, over 1106 days. A mean un-certainty of 2.3 m s − is obtained. A relatively large-amplitudevelocity variation is observed, as shown in Figure 5. It is best fit-ted with a 103.95 day period. The orbit is eccentric ( e = C. Moutou et al.: The HARPS search for southern extra-solar planets
Fig. 2.
The radial-velocity curve of HD 20868 obtained withHARPS. Top: individual radial-velocity measurements (dots)versus time, and fitted orbital solution (solid curve); Middle:residuals to the fitted orbit versus time; Bottom: radial-velocitymeasurements with phase-folding, using the period of 380.85days and other orbital parameters as listed in Table 2. The K3 / Jup companion.and semi-amplitude K = − . Although the signal is veryclear and stable over more than 10 periods, the residuals to the fitare a ff ected by an additional jitter, of amplitude 15.3 m s − . Thisjitter was expected from the relatively young age (1 Gyr) and thehigh value of log R ′ HK (mean value is -4.68), which strongly sug-gests that stellar variability is observed in addition to the mainsignal. The O-C residuals do not show, however, a periodicity re-lated to the 12d rotation , which is not surprising over about 80rotation cycles of the star. The Lomb-Scargle periodogram ofthe residuals do show, however, a tendency for a curved driftthat could be a hint for a second, longer-period planet, andother periodic signals could be present but too weak to besignificant . When taken into account, the curved drift decreasesthe residual noise from 15 to about 10 m s − . More data in thefuture may therefore reveal more planets in this system, butthe present material is not conclusive in this respect . Fig. 3.
The radial-velocity curve of HD 73267 obtained withHARPS. Top: individual radial-velocity measurements (dots)versus time, and fitted orbital solution (solid curve). The star hasa companion of minimum mass 3.06 M
Jup and orbital period1260 days. Bottom: residual to the fitted orbit versus time.
Fig. 4.
The radial-velocity curve of HD 131664 obtained withHARPS. Top: individual radial-velocity measurements (dots)versus time, and fitted orbital solution (solid curve). It shows avery massive planetary companion of m sin i = Jup withan orbital period of 1951 days. Bottom: residual to the fitted orbitversus time.Figure 6 shows the bisector behaviour with respect to radialvelocity (top) and as a function of the fit residuals. The scatter ofthe bisector span is larger than for the other stars, with a value of11 m s − , and it confirms that we see some line profile variationswith time. The bisector slope does not correlate, however, withthe radial velocity, excluding the stellar variability to be the only . Moutou et al.: The HARPS search for southern extra-solar planets 5 Fig. 5.
The radial-velocity curve of HD 145377 obtained withHARPS. Top: individual radial-velocity measurements (dots)versus time, and fitted orbital solution (solid curve); Middle:residuals to the fitted orbit versus time; Bottom: radial-velocitymeasurements with phase-folding, using the period of 103.95days and other orbital parameters as listed in Table 2. The resid-ual jitter is due to stellar variability (expected from activity indi-cators) and shows no periodic trend. A planet of minimum mass5.76 M
Jup is evidenced.origin of the observed velocity variation. We also find no corre-lation between the residuals to the fitted orbit and the bisectorspan (Figure 6 bottom). Such a correlation, observed when theactivity is mainly related to spots, could have been used to cor-rect the radial velocities for stellar variability, as explained inMelo et al. (2007). Finally, as a test to the origin of the RV jit-ter, we observed HD 145377 in a sequence of 10 consecutive90s exposures, for which a standard deviation of 2.5 m s − is de-rived. The stellar jitter therefore does not come from short-termacoustic modes but rather from chromospheric activity features.The planetary companion of HD 145377 is a m sin i = Jup planet orbiting with a 103.95d period. The semi-majoraxis is 0.45 AU. The periastron distance is 0.34 AU which cor-responds to a transit probability of 0.14%.
Fig. 6.
The inverse bisector slope is plotted against the radial ve-locity of HD 145377 (top) and against the residuals to the fittedorbit (bottom). No correlation between these quantities is ob-served. Although the bisector varies in a similar scale as the fitresiduals, we cannot correct for spot-related activity. The ampli-tude of bisectors’ variations still remains small compared to therange of radial velocities.
Finally, the star HD 153950 was observed 49 times with HARPSfrom August 1st 2003 to June 26th 2008 (1791 day time span).The mean uncertainty of the velocity measurements is 2 m s − .The velocity variation with time is fitted with a Keplerian or-bit of 499.4 day period (Figure 7). It is again an eccentric orbitwith e = − . The bisec-tor is rather flat over time and does not correlate with the orbitalphase nor the position of the velocity peak. The residuals aroundthe best solution have a standard deviation of 4 m s − and thereduced χ obtained for the fit is 2.40.This radial-velocity curve thus shows a planetary compan-ion of minimum mass 2.73 M Jup . Its semi-major axis is 1.28 AU.The orbit and planetary parameters of the six new systemsdescribed above are given with their inferred errors in Table 2.
4. Conclusion
From long-term observations with HARPS with individual un-certainty around 2 m s − , we were able to derive the presenceof 6 new substellar companions around the main-sequence starsBD -17 0063, HD 20868, HD 73267, HD 131664, HD 145377,and HD 153950.The analysis of the HARPS cross-correlation function and inparticular the bisector span of each measurement, allows to dis-card long-term stellar variability as the origin of the observedradial-velocity curve. This proved e ffi cient even for the mostactive star, HD 145377: characterizing the planetary companion C. Moutou et al.: The HARPS search for southern extra-solar planets
Table 2.
Orbital and physical parameters for the planets presented in this paper. T is the epoch of periastron. σ (O-C) is the residualnoise after orbital fitting of the combined set of measurements. χ red is the reduced χ of the fit. Parameter BD -17 0063 b HD 20868 b HD 73267 b HD 131664 b HD 145377 b HD 153950 b P [days] 655.6 (0.6) 380.85 (0.09) 1260. (7) 1951. (41) 103.95 (0.13) 499.4 (3.6) T [JD-2400000] 54627.1 (1.5) 54451.52 (0.1) 51821.7 (16) 52060. (41) 54635.4 (0.6) 54502. (4.3) e γ [km s − ] 3.026 (0.0012) 46.245 (0.0003) 51.915 (0.0005) 35.243 (0.004) 11.650 (0.003) 33.230 (0.001) ω [deg] 112.2 (1.9) 356.2 (0.4) 229.1 (1.8) 149.7 (1.0) 138.1 (2.8) 308.2 (2.4) K [m s − ] 173.3 (1.7) 100.34 (0.42) 64.29 (0.48) 359.5 (22.3) 242.7 (4.6) 69.15 (1.2) a sin i [10 − AU] 8.76 2.305 7.196 49.678 2.2074 2.981 f ( m ) [10 − M ⊙ ] 209.0 11.26 31.324 4295.665 132.788 14.174 m sin i [M Jup ] 5.1 (0.12) 1.99 (0.05) 3.06 (0.07) 18.15 (0.35) 5.76 (0.10) 2.73 (0.05) a [AU] 1.34 (0.02) 0.947 (0.012) 2.198 (0.025) 3.17 (0.03) 0.45 (0.004) 1.28 (0.01) N meas
26 48 39 41 64 49
S pan [days] 1760 1705 1586 1463 1106 1791 σ (O-C) [m s − ] 4.1 1.7 1.7 4.0 15.3 3.9 χ red Fig. 7.
The radial-velocity curve of HD 153950 obtained withHARPS. Top: individual radial-velocity measurements (dots)versus time, and fitted orbital solution (solid curve); Middle:residuals to the fitted orbit versus time; Bottom: radial-velocitymeasurements with phase-folding, using the period of 499.4days and other orbital parameters as listed in Table 2. The plan-etary companion has a minimum mass of 2.73 M
Jup . Fig. 8.
The present mass-period diagram of known exoplanets(open circles) showing the location of the six new planets pre-sented in this paper (filled circles). They belong to the bulge ofthe most massive, longest period bodies.does not su ff er too much from the stellar variability, because ofthe planet’s relatively short period with respect to our long timespan of observations (104 versus 1106 days). The stellar activityhere translates into a residual jitter that does not hide the planet’ssignal.The planet orbiting HD 131664 is very massive, with a min-imum mass of 18.15 M Jup , over the deuterium limit. It has char-acteristics similar to the other massive planet in distant orbitHD 168443 c (Udry et al. 2002), except that no internal planetto the system of HD 131664 is evidenced so far. The period ofHD 131664 b (1951 days or 5.34 years) is also among the dozenlongest known so far. Depending on the actual system age ofHD 131664, the magnitude di ff erence with the parent star couldbe as low as 13.5 in the K band – for the lower edge of the agerange – and up to 20, using the models of Bara ff e et al. (2002) forluminosity estimates. The angular separation ranges from 0.035to 0.16 arcsec during the orbit. Depending on the system’s incli-nation – and thus the true mass of the companion – it may be atarget for future direct imaging investigations, that would permita better characterisation of this unusual system. Note also thatthe parent star is particularly metal-rich ([ Fe / H ] = . Moutou et al.: The HARPS search for southern extra-solar planets 7 The rare combination of parameters for this system – compan-ion’s mass, orbital period, star’s metallicity – could make it oneimportant piece of constraints for theories of planetary forma-tion. Getting astrometric measurements of the six new systemswith VLTI / PRIMA would probably be possible, in order to bet-ter constrain their true mass.The new planets discussed in this paper are part of the bulgeof long period, massive extrasolar planets in eccentric orbits,with masses in the range 2-6 M
Jup and periods of 0.3 to 5.3years. Their properties can be discussed in the frame of thestatistical studies performed in well-defined stellar samples asin the ELODIE, CORALIE, or Lick + Keck + AAT surveys (seeMarcy et al. (2005) and Udry & Santos (2007) for in-depth dis-cussions): – Giant gaseous planets are found around about 6-7% ofknown main-sequence stars, with semi-major axes up toabout 5 AU. These six new planets contribute to increasethe number of known systems, with today 15 planets overthe 850 stars of the volume-limited sample monitored byHARPS. The 1.8% frequency of planet occurence in thissample where observations started in 2003, is, however, notyet at the level of the oldest surveys. Identically, only fivehot Jupiters were discovered in our sample, representing afrequency of 0.6%, to be compared to 1.2% frequency formore complete surveys. The new planet sample presented inthis paper yet contains the longest periods found in this spe-cific survey, with measurements obtained at the earliest agesof HARPS operations (Figure 8). – The distribution of planet masses currently favors the smallmasses, despite the strong observational bias towards mas-sive planets. Here we bring new evidence for planets in thehighest mass edge, with minimum masses of 2 to 18 M
Jup (Figure 8). – The period and eccentricity properties of the six new planetsconfirms the global tendency of very dispersed eccentrici-ties beyond the circularization zone due to tidal interactions,compared to the circular orbits of giant and distant planetsin the Solar System. The origin of such dispersed eccentric-ities remains a mystery despite a number of theoretical at-tempts to match the observed distribution from a variety ofeccentricity-damping physical processes. – Host stars of systems with giant gaseous planets are sig-nificantly more metal-rich than average (Santos et al. 2005;Fischer & Valenti 2005), which is not debated by the newexoplanet sample presented here, with two stars having anexcess metallicity compared to the Sun and no metal-poorplanet-host star. – About 12% of systems with gaseous giant planets are mul-tiple. Here, we find no indication for a second body in anyof the new systems, with a very small scatter of the residu-als of the order of a few m s − (except for HD 145377 whichis active). In order to find planets of lower mass in thesesystems, a high-precision strategy should now be applied.Finding larger distance planets in these systems is also pos-sible, although no significant long-term drift is yet observed. – Finally, the mass-period distribution of the six new plan-ets corroborates with the more general properties thatmore massive planets have longer orbital distances (e.g.,Udry & Santos (2007)).Adding new extrasolar systems to the ∼
300 planets knownsofar is of course of great importance to better characterize theirproperties. Radial-velocity survey, as well as transit-search pro-grams, su ff er the observational bias of detecting more easily the short-period and massive planets -the rarest ones-, which maybe the reason why only 6-7% of planets in the solar neighbour-hood show the signature of a giant planet. Note that this pro-portion of stars with planetary systems greatly increases whenplanets in the mass range of Neptune or below are discovered(Mayor & Udry 2008). Extending the planet sample, especiallyin well-defined volume-limited samples of main-sequence starsas monitored by HARPS, is one of the new challenges of this sci-entific field, to help understanding the mechanisms which formand maintain planets around other stars. Acknowledgements.
N.C.S. would like to thank the support from Fundac¸˜ao paraa Ciˆencia e a Tecnologia, Portugal, through programme Ciˆencia 2007 (C2007-CAUP-FCT / / ff for their support duringobservations. References
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Table 3.
Radial velocity values for BD -17 0063.
JD-2,400,000. Radial Vel. Uncertainty[km s − ] [km s −1
JD-2,400,000. Radial Vel. Uncertainty[km s − ] [km s −1 ]52943.610509 3.03585 0.0025853295.753206 3.04876 0.0017453945.903440 3.07611 0.0011153946.823277 3.06712 0.0014153951.864680 3.04030 0.0025253979.874025 2.88551 0.0019454082.599768 2.90011 0.0017454084.574580 2.90735 0.0019254346.836046 3.07882 0.0010754349.792760 3.07641 0.0013254427.598625 3.12206 0.0014954430.603057 3.12502 0.0014054437.605063 3.12820 0.0013754446.614295 3.13480 0.0016454478.592373 3.14747 0.0015554486.529176 3.14468 0.0017454609.910593 3.03512 0.0015554637.911547 2.85740 0.0013654641.924906 2.85339 0.0011554646.887252 2.83517 0.0013054657.823636 2.82295 0.0010154670.790307 2.81336 0.0013954672.838582 2.81770 0.0018354698.807055 2.84664 0.0014954701.823517 2.85211 0.0017754703.858883 2.85025 0.00162. Moutou et al.: The HARPS search for southern extra-solar planets , Online Material p 3
Table 4.
Radial velocity values for HD 20868.
JD-2400000. Radial Vel. Uncertainty[km s − ] [km s −1
JD-2400000. Radial Vel. Uncertainty[km s − ] [km s −1 ]52944.759761 46.30911 0.0025553578.941288 46.21963 0.0016553579.927242 46.21953 0.0013553668.773536 46.28134 0.0015053670.728503 46.28763 0.0014553672.797736 46.29419 0.0014853674.743782 46.30446 0.0013553675.819517 46.31087 0.0011453691.577515 46.41910 0.0015553721.706478 46.26692 0.0013553724.633943 46.26712 0.0011853725.585119 46.26338 0.0011353762.579524 46.23860 0.0014553764.539118 46.23716 0.0011353974.869681 46.22482 0.0023253979.923748 46.22749 0.0020053981.897310 46.22813 0.0015554079.673981 46.35546 0.0013554083.717877 46.33114 0.0015454314.874429 46.22101 0.0014954345.833998 46.22372 0.0012654347.832433 46.22375 0.0011954386.726662 46.23193 0.0015154394.752760 46.23539 0.0020754421.692913 46.26423 0.0010254428.736985 46.27712 0.0012154430.633523 46.28286 0.0011254437.676734 46.31306 0.0013854438.644277 46.31772 0.0015454445.632867 46.37310 0.0015254446.708327 46.38629 0.0014954447.647299 46.39631 0.0017354448.662135 46.40572 0.0019154449.673081 46.41303 0.0014454450.625557 46.41899 0.0013154451.657624 46.42038 0.0017554452.629288 46.42265 0.0017854453.668760 46.41719 0.0014054454.671103 46.40928 0.0016954478.640303 46.27767 0.0010654486.573877 46.26497 0.0014954525.518526 46.23992 0.0013754638.948171 46.21787 0.0014954640.934733 46.22498 0.0020654643.941030 46.22350 0.0015154645.930747 46.21843 0.0012154647.933071 46.22028 0.0013354649.925384 46.22170 0.00129. Moutou et al.: The HARPS search for southern extra-solar planets , Online Material p 4
Table 5.
Radial velocity values for HD 73267.
JD-2400000. Radial Vel. Uncertainty[km s − ] [km s −1
JD-2400000. Radial Vel. Uncertainty[km s − ] [km s −1 ]53031.730610 51.84750 0.0021453034.625318 51.84718 0.0017153374.800416 51.96412 0.0013153410.705484 51.96753 0.0013053469.507660 51.96638 0.0017553699.856836 51.94628 0.0015353762.700039 51.93917 0.0012053781.723770 51.92696 0.0056553789.716242 51.93850 0.0020254077.853694 51.86690 0.0011754084.808437 51.86669 0.0015454121.750283 51.85900 0.0010754167.636520 51.84519 0.0013454173.606470 51.84531 0.0018854232.560360 51.84650 0.0023154233.545820 51.83822 0.0014854234.516188 51.84184 0.0019154255.451119 51.84149 0.0020754257.498753 51.83751 0.0024854258.452112 51.84183 0.0017054392.856053 51.88474 0.0019254393.861259 51.88672 0.0018354420.846468 51.90180 0.0013454427.833648 51.90648 0.0014854431.832778 51.90942 0.0015754446.853818 51.91236 0.0017254478.822609 51.92923 0.0013854486.729809 51.93068 0.0018554520.667295 51.94426 0.0016754521.641787 51.94405 0.0020854547.580289 51.95049 0.0014454548.606686 51.95113 0.0018454554.625472 51.95626 0.0014654555.617466 51.95268 0.0016154582.554316 51.95708 0.0020954593.487209 51.96142 0.0014854609.467804 51.96419 0.0014254616.504677 51.96460 0.0011154618.463621 51.96406 0.00157. Moutou et al.: The HARPS search for southern extra-solar planets , Online Material p 5
Table 6.
Radial velocity values for HD 131664.
JD-2400000. Radial Vel. Uncertainty[km s − ] [km s −1
JD-2400000. Radial Vel. Uncertainty[km s − ] [km s −1 ]53146.689878 35.36621 0.0023553150.721130 35.37138 0.0019453506.661928 35.40323 0.0032853515.682762 35.41041 0.0029153516.706183 35.40838 0.0038053544.650439 35.40707 0.0012953575.529526 35.41260 0.0020453765.883247 35.35969 0.0014853789.862142 35.34722 0.0020053790.891695 35.34791 0.0023453831.878129 35.30995 0.0019153833.894708 35.31519 0.0025153834.793072 35.31172 0.0017953835.766752 35.31675 0.0019253862.689370 35.28105 0.0022253869.760171 35.26920 0.0022653882.633600 35.24120 0.0016053886.645454 35.23779 0.0018954141.891213 34.87671 0.0016054169.833067 34.94571 0.0018654173.842331 34.94933 0.0018354194.919509 34.98657 0.0019454197.764290 34.98699 0.0015654199.875525 34.98575 0.0018654202.767256 34.99557 0.0015554225.722932 35.01516 0.0029154253.647281 35.06246 0.0029254257.633280 35.05809 0.0020354258.634595 35.05959 0.0016754259.617251 35.06109 0.0027054316.466834 35.10819 0.0026154521.868941 35.23283 0.0006154523.843516 35.22223 0.0037654528.845576 35.22825 0.0023254547.737400 35.23304 0.0023654548.830829 35.23871 0.0022254554.803145 35.24746 0.0006054555.817248 35.24875 0.0006054557.770244 35.25325 0.0007154582.619078 35.24712 0.0022254609.613271 35.26701 0.00185. Moutou et al.: The HARPS search for southern extra-solar planets , Online Material p 6
Table 7.
Radial velocity values for HD 145377.
JD-2400000. Radial Vel. Uncertainty[km s − ] [km s −1
JD-2400000. Radial Vel. Uncertainty[km s − ] [km s −1 ]53542.633832 11.77595 0.0017053544.730958 11.81187 0.0023853546.751703 11.78922 0.0018153550.654537 11.83375 0.0014353551.609534 11.81601 0.0017353573.602135 11.82109 0.0036753574.531691 11.81516 0.0024153575.546089 11.80329 0.0021153576.546067 11.80878 0.0026853578.665360 11.75643 0.0023253861.783012 11.78616 0.0022453862.741865 11.77693 0.0023153863.749757 11.78931 0.0031353864.742775 11.80499 0.0031553865.771405 11.81063 0.0017053866.724997 11.81256 0.0022353867.778590 11.82035 0.0011953868.748140 11.82455 0.0011453870.593760 11.82535 0.0014853871.786449 11.80792 0.0008553882.713288 11.79242 0.0015453887.717218 11.78144 0.0017353889.679215 11.79304 0.0029053920.603556 11.35688 0.0026453945.583464 11.66717 0.0012554143.897228 11.59350 0.0022754166.891741 11.77823 0.0036754168.883742 11.80202 0.0020054172.857726 11.79734 0.0019254174.848564 11.81779 0.0019654194.917474 11.79477 0.0017354199.899854 11.76678 0.0020554202.889292 11.73950 0.0019054229.719267 11.33710 0.0036854234.652538 11.40673 0.0025754253.744628 11.65247 0.0039954254.678126 11.66130 0.0027554255.722560 11.67890 0.0026454259.725812 11.70184 0.0034054261.794683 11.70275 0.0090154313.620619 11.64514 0.0023254315.497608 11.61620 0.0012954316.611584 11.59821 0.0015654317.496297 11.55722 0.0008354319.542744 11.49931 0.0010254320.580289 11.47979 0.0011154323.537296 11.43111 0.0013854346.502395 11.50437 0.0025354347.501198 11.51593 0.0026754349.526984 11.54072 0.0022654523.859926 11.57233 0.0025454528.878747 11.46067 0.0030354547.759621 11.43022 0.0018654548.852149 11.44839 0.0026954550.842175 11.48418 0.0021054552.800759 11.50967 0.0023354553.821042 11.51551 0.0022654556.798027 11.56205 0.0018654568.811680 11.70450 0.0017254582.623731 11.78479 0.0028454609.642688 11.84143 0.0004054637.784021 11.37846 0.0070854643.725606 11.35829 0.0013654648.688288 11.41413 0.00140. Moutou et al.: The HARPS search for southern extra-solar planets , Online Material p 7
Table 8.
Radial velocity values for HD 153950.
JD-2400000. Radial Vel. Uncertainty[km s − ] [km s −1