Mon.Not.R.Astron.Soc.000,1–10(2016) Printed30January2017 (MNLATEXstylefilev2.2) Mg, Al, Si, Ca, Ti, Fe, and Ni abundance for a sample of solar analogues 7 ⋆ 1 Ricardo L´opez-Valdivia , Emanuele Bertone, and Miguel Cha´vez 0 Instituto Nacional de Astrof´ısica, O´ptica y Electro´nica, Luis Enrique Erro 1, Tonantzintla, Puebla, 72840, M´exico 2 n a Accepted XXX.ReceivedYYY;inoriginalformZZZ J 6 2 ABSTRACT We reportonthe determinationofchemicalabundancesof38solaranalogues,includ- ] R ing 11 objects previously identified as super metal-rich stars. We have measured the equivalent widths for 34 lines of 7 different chemicalelements (Mg, Al, Si, Ca, Ti, Fe, S andNi)inhigh-resolution(R∼80000)spectroscopicimages,obtainedattheObserva- . h torioAstrof´ısicoGuillermo Haro(Sonora,Mexico),with the CananeaHigh-resolution p Spectrograph. We derived chemical abundances using ATLAS12 model atmospheres - andtheFortrancodeMOOG.Weconfirmedthesupermetallicitystatusof6solarana- o r logues.Withinoursample,BD+60600isthemostmetal-richstar([Fe/H]=+0.35dex), t while for HD 166991we obtained the lowestironabundance ([Fe/H]=−0.53dex). We s a also computed the so-called [Ref] index for 25 of our solar analogues, and we found, [ that BD+60 600 ([Ref]=+0.42) and BD+28 3198 ([Ref]=+0.34) are good targets for exoplanet search. 1 v Key words: stars: solar-type; stars: abundances; techniques: spectroscopic. 0 5 8 7 0 1 INTRODUCTION Thepresentworkisthecontinuationofaglobalproject . 1 aimed at determining atmospheric parameters and chem- Stellar chemical composition represents an important pa- 0 ical abundances of solar analogues (main sequence stars rameter in stellar and galactic astronomy studies, and, in 7 with spectral types between G0 and G3)1, with special in- particular, in the relatively recent field of exoplanets. In 1 terest in looking for giant exoplanet host star candidates. this latter field, different studies have aimed at searching : In L´opez-Valdivia et al. (2014), we simultaneously deter- v for possible correlations between properties (mainly chemi- i mined the basic stellar atmospheric parameters [effective X calcomposition)ofhoststarsandtheoccurrenceofexoplan- temperature(T ),surfacegravity(logg),andglobalmetal- ets. Gonzalez (1997), with the search for exoplanets still in eff r licity ([M/H])], for a sample of 233 solar analogues, using a its early stages, suggested a link between high metal con- intermediate-resolutionspectra(R∼1700at4300˚A)anda tentofhoststarsandthepresenceofgiantgaseous planets. set of Lick-like indices defined within 3800–4800 ˚A. We de- Suchcorrelation was laterconfirmedbyotherauthors(e.g., termined for the first time the atmospheric parameters for Fischer & Valenti 2005; Johnson et al. 2010; Sousa et al. 213 stars, of which 20 are new super metal-rich star candi- 2011)anditagreeswiththecoreaccretiontheoryforplanet dates (SMR;[M/H]≥0.16 dex). formation (Pollack et al. 1996; Alibert, Mordasini & Benz The second goal of our project is the analysis of chem- 2004),wherehighmetallicity facilitates theformation ofgi- ical abundances, which we started with the determina- ant gas planets. tion of the lithium abundance of a sample of 52 stars Within this scenario, the iron abundance ([Fe/H]) is (L´opez-Valdiviaet al. 2015). The analysis was carried out commonly used as proxy for overall metallicity; however, usingnarrowbandhigh-resolutionspectra(R∼80000)cen- Gonzalez (2009) suggested the use of a new metallicity in- tredonthe6708˚Alithiumfeature.Thissampleincluded12 dex, called [Ref], which takes into account the mass abun- SMRobjects from ourprevious work (L´opez-Valdivia et al. danceof therefractory elements Mg, Si, and Fe,since their 2014). number densities and condensation temperatures are very In this third part of the series, we complement the similar. This [Ref]indexismoresensitive(mainly atvalues lithiumabundancewiththechemicalabundancesofMg,Al, greater than +0.20 dex) than [Fe/H] to describe the inci- denceprobability of giant planetsorbiting a star (Gonzalez 2014). 1 In our sample the stars HD 130948 and HD 168874 have a different spectral type; nevertheless, we included them, because theiratmosphericparametersarecompatiblewiththerestofthe ⋆ E-mail:[email protected] sample. 2 L´opez-Valdivia R., Bertone E. & Ch´avez M. Si, Ca, Ti, Fe, and Ni, for 38 solar analogues. The sample our star. We found ξ values between 0.83 and 1.63 kms−1, and the observations are described in Section 2. In Section which are in agreement with values determined from syn- 3, we detail the determination of the chemical abundances, theticspectra (Husseret al. 2013). and, in Section 4, we discuss theresults. Regarding the atmospheric parameters uncertainties, we used those reported in L´opez-Valdivia et al. (2015). For those cases where uncertainties were not available, we as- signed, for logg and ξ, ± 0.27 dex and ± 0.27 kms−1, as 2 STELLAR SAMPLE AND OBSERVATIONS the typical uncertainty, which is the standard deviation of We selected 38 objects among the brightest stars of both logg and ξ distributions of the Takeda’s stars with L´opez-Valdivia et al. (2015). In Table 1, we list the name T within the values of our sample. For the uncertainty of eff of thestar, thevisual magnitude,thespectral typeand the [M/H] we assumed ±0.10 dex as a conservativeerror. atmosphericparameters(andtheiruncertainties)fortheen- Usingtheatmospheric parameters reported in Table 1, tire sample. The spectroscopic data were collected at the wecomputedanATLAS12(Kurucz2013)modelatmosphere 2.1 m telescope of the Observatorio Astrof´ısico Guillermo for each star; we also computed a solar model atmosphere Haro,locatedinMexico,usingtheCananeaHigh-resolution withTeff,⊙=5777K,logg⊙=4.44dex,[M/H]⊙=0.0dex,and Spectrograph(CanHiS).CanHiSisequippedwithmid-band ξ⊙=1.0 kms−1. filters, thatprovideaccess to∼40 ˚Awide wavelength inter- vals in a single diffraction order. We observed the entire sample with a spectral resolv- 3.2 Line list ing power of R∼ 80000 and a typical signal-to-noise ratio We extracted the atomic transitions between 4995 and (S/N)ofabout 100,using4differentfiltersofCanHiS,cen- tred at 5005, 5890, 6310, and 6710 ˚A, respectively, giving 6730 ˚A from The Viena Atomic Line Database (VALD, Piskunov et al. 1995; Kupkaet al. 1999), using the atmo- access to lines of Mg, Al, Si, Ca, Ti, Fe, and Ni (Fig. 1). sphericparametersoftheSun.Withtheseatomictransitions We also obtained the solar spectrum reflected by the aster- and the ATLAS12 solar model, we created with SYNTHE oid Vesta with the same instrumental setup. Per filter and (Kurucz& Furenlid 1979; Kurucz& Avrett 1981; Kurucz perstar,wecollected atleast3exposures,resultingintotal 1993) a syntheticsolar spectrum at the same spectral reso- exposure times between 1.5 and 3 hours. lution as our observations. From theVestaspectrum we se- Data reduction was conducted following the standard lected 34 suitable atomic lines (listed in Table 2 and shown procedures of IRAF: bias subtraction, flat-field correction, in Fig. 1) of 7 different chemical elements (Mg, Al, Si, Ca, cosmic-ray removal, wavelength calibration through an in- Ti,Fe,andNi),avoidingweakorsaturatedlinesandblends. ternal UNe lamp, and, finally, continuum normalization. Neveset al.(2009)pointedoutthatoscillatorstrengths We then shifted all the spectra to the rest frame, using a (loggf) of VALD might not be accurate enough for all the degraded (to our resolution) version of the high-resolution atomic transitions. To correct these possible inaccuracies, spectrum of the Sun (Kuruczet al. 1984) as template. For we determined theEW (see Section 3.3) for the34 selected eachstar(andfilter)weco-addedsingleexposuresweighted linesintheobservedandsyntheticsolarspectrum;then,we by theS/N to obtain thefinal spectrum. compared both measurements and we modified the loggf until both measurements (observed and synthetic) agreed. For15lines,wealsoslightlymodifiedthecentralwavelength 3 ABUNDANCES DETERMINATION reported by VALD. The transition parameters from VALD We determined the chemical abundances, through a local as well as their modifications are reported in Table 2. thermodynamicequilibrium(LTE)analysis,usingthedriver abfind of the February 2013 version of MOOG (Sneden 1973), which performs an adjustment of the abundance to 3.3 Equivalent widths matchasingle-lineequivalentwidth(EW).MOOGrequires The EW determination plays a fundamental role in the astandardsolarcomposition(weusedthesolarabundances abundance determination. Since the EW depends strongly ofGrevesse & Sauval1998),amodelatmosphere,alinelist, on the local continuum level, it is of crucial importance to and an EW measurement to compute atomic abundances. determineit as accurately aspossible. Weimplemented the Below we describe in detail each of theserequirements. following procedure to establish the local continuum level and to measure theEW. First,bymeansofaGaussianfitofasmallregion(5˚A), 3.1 Photospheric parameters and model weidentifiedandremovedthepointsthatform thespectral atmospheres lineofinterest,whicharepointsenclosedinaintervalof±3σ Inordertocomputeamodelatmospherethebasicparame- from the central wavelength of the line. Then, we passed tersarerequired:T ,logg,[M/H],andthemicroturbulence throughaniterativeroutinetheremainingspectrum,which eff velocity (ξ). We adopted the T , logg, and [M/H] values is acombination of neighbouring lines andnoise, toremove eff ofourpreviouswork(L´opez-Valdivia et al.2015).Forξ,we pointsabove±2σtheiraveragevalueinordertoidentifythe used the grid of atmospheric parameters of Takeda et al. localcontinuum.Finally,weadjustedtothelineaGaussian (2005), which includes determination of T , logg, [M/H], profile whose integral represents its EW. eff andξfor160FGKstars.WelookedwithintheTakeda’sgrid We estimated the error on the EW applying a Monte thenearest set ofthefirst 3parameters foreach star inour Carlo methodwith 1000 iterations, randomlyaddingtothe sample,andweassigned theTakeda’sdetermination ofξ to spectrum the noise of the local continuum. Chemical abundances in a sample of solar analogues 3 Ni Ti NiFeTi Ti NiFe Fe Ni Ni Ti 1.0 0.6 0.2 −0.2 −0.6 4995 5000 5005 5010 5015 5020 FeSi Fe Fe Ti Fe 1.0 0.6 t e s 0.2 f f o −0.2 + x −0.6 u fl 5870 5875 5880 5885 5890 5895 5900 5905 d e Fe Fe Fe Mg NiFe z 1.0 i l a m 0.6 or 0.2 n −0.2 −0.6 6290 6295 6300 6305 6310 6315 6320 6325 Al Fe Fe Fe FeFeFe Ca Si Fe 1.0 0.6 0.2 −0.2 −0.6 6690 6695 6700 6705 6710 6715 6720 6725 6730 wavelength (A˚) Figure 1. Normalized spectra of Vesta (black), HD 12699 (gray), and BD+28 3198 (light gray) in the four spectral regions, with identificationoftheatomiclinesusedtocomputeabundances.Notethattheintervalcentredat6310˚Aismoreaffectedbythepresence oftelluriclines. Wecheckedtheconsistency of ourprocedurebymeans thelineswhosebestfitwasnotaccurateenough;theselines of a comparison of solar line EWs determined in two differ- vary from star to star. The EWs of Table 3 were used in entworks(Neveset al.2009;Takeda et al.2005)withthose MOOG to compute the chemical abundances. For species determined by us. We measured in the solar spectrum of with more than one analysed transition, we carried out a Kuruczet al. (1984), also used by Takeda and Neves, the weighted mean to obtain the final abundance, after having EWfor57and178ironlinesreportedbyTakeda et al.2005 discarded outliers with an iterative 3σ clipping. and Neveset al. 2009, respectively. From this comparison, It is important to note that these two rejection which is depicted in Fig. 2, we found good agreement, with processes could introduce potential biases and different some small differences, which can be explained by different abundance scales in stars with different excluded lines. local continuum levels. The first filter is actually a visual inspection that relies on the S/N of the spectra and is not directly associated with abundances, while the sigma clipping is indeed applied 3.4 Abundances computation and error budget. directly to abundances, but it was employed in only one For each star and Vesta, we measured the EW of all lines Fe line of eight stars. In order to take into account these listed in Table 2. We rejected, through visual inspection, potential biases, we conducted a Monte Carlo procedure 4 L´opez-Valdivia R., Bertone E. & Ch´avez M. Table1.Atmosphericparametersandtheiruncertaintiesofthestellarsample.Forallthestarsofoursampletheerror onthemicroturbulencevelocityis0.27kms−1. Object V SType Teff σ logg σ [M/H] σ ξ (K) (K) (dex) (dex) (dex) (dex) (kms−1) HD5649 8.70 G0V 5830 52 4.45 0.22 -0.08 0.04 1.03 BD+60402 10.26 G0V 5985 72 4.30 0.40 0.22 0.09 1.15 HD16894 8.02 G2V 5500 70 4.05 0.30 -0.10 0.09 0.83 BD+60600 8.65 G0V 5655 47 3.95 0.20 0.20 0.07 1.18 HD232824 9.52 G2V 5900 67 4.15 0.35 0.16 0.08 1.27 HD237200 9.66 G0V 6045 55 4.25 0.32 0.18 0.05 1.26 HD26710 7.18 G2V 5815 47 4.55 0.20 -0.04 0.04 1.63 HD31867 8.05 G2V 5590 57 4.40 0.25 -0.10 0.06 0.98 HD33866 7.87 G2V 5481 123 4.33 0.27 -0.07 0.10 0.91 HD41708 8.03 G0V 5998 58 4.55 0.27 0.08 0.10 1.33 HD42802 6.44 G2V 5617 80 4.53 0.27 -0.11 0.10 0.98 HD77730 7.39 G2V 5698 80 4.13 0.27 -0.05 0.10 1.00 HD110882 8.87 G1V 5880 50 4.40 0.25 -0.28 0.04 1.14 HD110884 9.11 G3V 5905 87 4.30 0.40 -0.26 0.08 1.16 HD111513 7.35 G1V 5723 80 4.31 0.27 0.12 0.10 1.21 HD111540 9.54 G1V 5840 47 4.20 0.25 0.14 0.05 1.13 HD124019 8.56 G2V 5685 57 4.65 0.25 -0.18 0.06 0.88 HD126991 7.90 G2V 5360 107 3.15 0.40 -0.34 0.14 1.27 HD129357 7.83 G2V 5775 52 4.30 0.22 -0.14 0.05 1.21 HD130948 5.88 F9IV-V 5885 80 4.42 0.27 -0.09 0.10 1.28 HD135145 8.35 G0V 5997 80 4.14 0.27 -0.02 0.10 1.19 HD135633 8.46 G0V 6095 67 4.25 0.40 0.22 0.06 1.27 HD140385 8.57 G2V 5735 60 4.60 0.27 -0.16 0.08 1.13 HD145404 8.54 G0V 5920 82 4.43 0.27 -0.16 0.10 1.20 HD152264 7.74 G0V 6177 73 4.09 0.27 0.02 0.10 1.36 BD+292963 8.42 G0V 5865 55 4.70 0.22 0.00 0.04 1.27 HD156968 7.97 G0V 6105 96 4.42 0.27 -0.03 0.10 1.30 HD168874 7.01 G2IV 5696 80 4.41 0.27 -0.05 0.10 0.86 BD+283198 8.66 G2V 5840 35 4.00 0.17 0.24 0.05 1.25 TYC2655-3677-1 9.93 G0V 6220 47 4.15 0.27 0.28 0.05 1.31 HD333565 8.75 G1V 5990 52 4.45 0.27 0.12 0.05 1.19 HD228356 9.07 G0V 6055 37 4.00 0.20 0.16 0.05 1.41 HD193664 5.93 G3V 5942 112 4.47 0.27 -0.11 0.10 1.28 BD+473218 8.70 G0V 6050 52 4.05 0.30 0.16 0.06 1.41 HD210460 6.19 G0V 5357 80 3.58 0.27 -0.17 0.10 1.27 TYC3986-3381-1 10.37 G2V 5855 57 4.15 0.25 0.26 0.07 1.15 HD212809 8.64 G2V 5975 55 4.55 0.27 0.16 0.05 1.33 BD+284515 8.73 G2V 5580 40 3.50 0.17 -0.22 0.06 1.29 in which we computed the Fe, Ni, and Ti abundance 140 (elementswith moreavailable lineswithin ourlinelist with Nevesetal.2009 18, 6, and 5, respectively) for Vesta and some stars of our Takedaetal.2005 120 sample. We computed the mean abundance of Fe, Ni, and Ti using different size sets of randomly selected lines. After 100 1000 iterations for each set, element, and star, we demon- ˚Am) 80 strated that the final abundance of these elements in all ( thecasesdoesnotchangebymorethan0.02dexonaverage. T WLI 60 E We report in Table 4 the abundances of the 7 atomic 40 elements for our sample; they are given with respect to the solar abundances determined for Vesta2 (see Table 5). 20 TheTablealso providestheabundanceuncertaintyandthe numberof lines used for theabundancedetermination. 0 0 20 40 60 80 100 120 140 EWTW(mA˚) Figure 2. Comparison of the solar EW computed in this study (EWTW) and those determined by Takedaetal. (2005) and Nevesetal.(2009). 2 [X/H] = A(X)star - A(X)⊙, where A(X)⊙ is the computed abundance forVesta. Chemical abundances in a sample of solar analogues 5 Table 2. Set of atomic parameters from VALD and the modifi- Table 3. EWs of the atomic lines considered for abundance de- cationsmadebyustothecentralwavelength andtheloggf. termination.ThecompleteTableisavailableinelectronicversion. λ ∆λ element χ loggf ∆loggf Star λ Ele. EW σ (˚A) (˚A) (eV) (˚A) (m˚A) (m˚A) 4995.650 0.005 NiI 3.635 -1.580 -0.308 HD5649 4998.224 28 27.35 2.51 4997.098 - TiI 0.000 -2.070 -0.156 HD5649 4999.510 22 59.01 2.77 4998.224 - NiI 3.606 -0.700 -0.261 HD5649 5000.992 22 24.08 3.18 4999.112 - FeI 4.186 -1.740 -0.066 HD5649 5006.130 26 124.59 5.58 4999.503 0.007 TiI 0.826 0.320 -0.279 HD5649 5010.940 28 23.02 2.81 5000.990 0.002 TiI 1.997 -0.020 -0.255 HD5649 5016.165 22 24.09 3.35 5003.741 0.003 NiI 1.676 -3.070 -0.265 HD5649 5877.788 26 8.71 1.16 5004.044 - FeI 4.209 -1.400 -0.110 HD5649 5880.027 26 10.47 1.57 5006.119 0.011 FeI 2.833 -0.638 -0.336 HD5649 5905.674 26 30.81 1.62 5010.023 - NiI 3.768 -0.980 -0.085 HD5649 6297.794 26 47.92 1.26 5010.938 0.002 NiI 3.635 -0.870 -0.161 HD5649 6322.689 26 49.03 1.82 5016.161 0.004 TiI 0.848 -0.480 -0.294 ... ... ... ... ... 5873.212 - FeI 4.256 -2.140 0.168 5873.763 - SiI 4.930 -4.244 1.194 5877.788 - FeI 4.178 -2.230 -0.009 4 DISCUSSION 5880.027 - FeI 4.559 -1.940 -0.028 5899.293 - TiI 1.053 -1.100 -0.098 4.1 Super metal rich stars and the [Ref] index 5905.671 0.003 FeI 4.652 -0.730 -0.179 In our working sample, we included 11 stars considered as 6293.925 - FeI 4.835 -1.717 -0.083 6297.792 0.002 FeI 2.223 -2.740 -0.185 SMR ([M/H] ≥ 0.16 dex) in L´opez-Valdivia et al. (2014). 6315.811 - FeI 4.076 -1.710 -0.023 From the present high-resolution analysis, we confirm the 6319.237 - MgI 5.108 -2.324 0.238 SMRstatus,bymeansoftheirironabundance,for6objects, 6322.166 0.003 NiI 4.154 -2.426 1.267 namely BD+60 402, BD+60 600, HD 237200, HD 135633, 6322.685 0.004 FeI 2.588 -1.170 -1.256 BD+28 3198, and TYC 3986-3381-1, while, for other 3 6698.673 - AlI 3.143 -1.647 -0.255 stars (BD+47 3218, HD 212809, HD 232824), we ob- 6703.566 0.003 FeI 2.759 -3.160 0.097 tain [Fe/H] lower than the SMR threshold. However, both 6705.101 0.003 FeI 4.607 -1.392 0.269 BD+47 3218 and HD 212809 have super-solar abundances 6710.318 - FeI 1.485 -4.880 0.036 for all atomic species and some of them are well above the 6713.046 - FeI 4.607 -0.963 -0.380 +0.16dexthreshold.ThetworemainingcasesofSMRstars, 6713.743 - FeI 4.796 -1.600 0.186 6715.382 - FeI 4.608 -1.640 0.109 HD 228356 and TYC 2655-3677-1, are discussed below. 6717.681 0.003 CaI 2.709 -0.524 0.025 The 6 SMR stars are therefore excellent targets to 6721.848 - SiI 5.863 -1.527 0.415 searchforgiantplanetcompanions.Inordertoquantifythe 6726.666 0.003 FeI 4.607 -1.133 0.078 probability of detecting these planets, we make use of the [Ref] index definedby Gonzalez (2009): Along with the uncertainty on the EW measurement, [Ref] = log(cid:0)24×107.55+[Mg/H]+28×107.53+[Si/H]+56 the error on the stellar parameters is the source that most (1) affects the final abundances. To properly assess it, we con- ×107.47+[Fe/H](cid:1)−9.538 structed a small matrix of abundance variations as a func- We report the [Ref] index and [Fe/H] in Table 6, tion of the difference in four atmospheric parameters (T , eff where we also provide the probability [P(%)] of hosting logg, [M/H], and ξ), taking the solar values as reference. a giant planet, obtained from the probability functions of Foreachabsorptionlinej,weconsideredtheEWmeasured Gonzalez (2014) and Fischer & Valenti (2005), based solely on the Vesta spectrum and we computed a grid of abun- on chemical composition considerations. BD+60 600 (39%) dance variations ∆[X/H]j = [X/H]j −[X/H]j,⊙, caused by and BD+28 3198 (22%) stand out as the best targets for a a difference ∆Teff,⊙ = 150 K, of ∆logg⊙ = 0.40 dex, of giant exoplanet search program. ∆[M/H]⊙ =0.20 dex,and of ∆ξ⊙ =0.50 kms−1.Then, for each star, we obtained the ∆[X/H] corresponding to each j atmospheric parameter by linearly interpolating this grid, 4.2 [X/Fe] behaviour and comparison with assuming,asparametervaluedifference,theerrorsreported literature data. in Table 1. The error on the abundance derived from each absorption line is the quadratic sum of the error on the at- In Figure 5, we show the [X/Fe] ratios for the elements in- mospheric parameters and theEW. cludedinouranalysis.Inordertocheckforconsistencywith other abundance studies on objects of the solar neighbour- hood,wecompareourresultswiththeworksofNeves et al. (2009), Adibekyanet al. (2012), and Hinkelet al. (2014), which include LTE abundances for FGKM main sequence stars, within a distance of 150 pc from the Sun. We found good agreement with theseprevious works. OurMg, Si, Ca andTiratiospresentahigherscatterthanAl,andNi,nev- 6 L´opez-Valdivia R., Bertone E. & Ch´avez M. Table 4. Chemical abundances of the stellar sample. For each element we present in different rows the weighted mean abundance, its error,andthenumberoflinesusedinthedeterminationoftheabundance perstar. Star [Mg/H] [Al/H] [Si/H] [Ca/H] [Ti/H] [Fe/H] [Ni/H] HD5649 – – – -0.48 -0.42 -0.32 -0.43 – – – 0.13 0.07 0.02 0.06 – – – 1 3 9 2 BD+60402 +0.18 +0.20 +0.20 +0.26 +0.17 +0.19 +0.16 0.12 0.04 0.04 0.19 0.06 0.02 0.04 1 1 1 1 4 15 5 HD16894 -0.21 – +0.25 +0.32 +0.07 +0.04 -0.01 0.05 – 0.08 0.17 0.06 0.02 0.04 1 – 1 1 4 16 6 BD+60600 +0.51 +0.39 +0.44 +0.51 +0.24 +0.35 +0.34 0.05 0.04 0.04 0.13 0.05 0.01 0.03 1 1 2 1 4 18 5 HD232824 -0.07 -0.08 -0.03 -0.07 -0.24 -0.09 -0.06 0.07 0.05 0.04 0.17 0.07 0.02 0.04 1 1 2 1 4 17 4 HD237200 +0.03 +0.13 +0.20 +0.27 +0.21 +0.18 +0.14 0.07 0.04 0.04 0.17 0.07 0.01 0.04 1 1 2 1 4 16 5 HD26710 -0.13 – +0.09 +0.08 -0.23 +0.08 -0.12 0.04 – 0.04 0.13 0.05 0.01 0.03 1 – 1 1 4 14 4 HD31867 -0.21 – +0.13 -0.06 -0.13 -0.07 -0.05 0.04 – 0.05 0.14 0.04 0.01 0.03 1 – 1 1 5 14 6 HD33866 -0.06 – – +0.04 -0.35 -0.22 -0.20 0.06 – – 0.17 0.08 0.02 0.04 1 – – 1 4 15 5 HD41708 +0.22 – – -0.03 +0.07 +0.08 +0.12 0.04 – – 0.16 0.05 0.01 0.03 1 – – 1 4 15 6 HD42807 +0.02 – +0.03 +0.06 -0.05 -0.10 -0.15 0.04 – 0.06 0.16 0.05 0.01 0.04 1 – 1 1 5 15 5 HD77730 -0.50 -0.18 -0.15 -0.30 -0.41 -0.40 -0.35 0.06 0.05 0.04 0.16 0.06 0.02 0.04 1 1 1 1 5 16 6 HD110882 -0.32 – – -0.31 -0.18 -0.37 -0.31 0.04 – – 0.14 0.05 0.02 0.04 1 – – 1 4 9 6 HD110884 – -0.17 – -0.11 -0.18 -0.14 -0.11 – 0.04 – 0.19 0.07 0.02 0.05 – 1 – 1 3 16 4 HD111513 +0.23 +0.03 +0.21 +0.08 -0.03 +0.04 +0.12 0.04 0.04 0.03 0.16 0.06 0.01 0.03 1 1 2 1 4 17 5 HD111540 +0.00 +0.17 +0.28 +0.24 +0.09 +0.13 +0.14 0.09 0.04 0.04 0.14 0.05 0.01 0.04 1 1 2 1 4 15 6 HD124019 -0.16 -0.15 +0.30 -0.17 -0.12 -0.05 -0.24 0.06 0.04 0.06 0.14 0.05 0.01 0.04 1 1 1 1 5 13 5 HD126991 -0.29 -0.20 -0.41 -0.20 -0.10 -0.53 -0.37 0.04 0.04 0.04 0.20 0.06 0.02 0.04 1 1 1 1 5 16 5 HD129357 -0.04 -0.01 – -0.03 +0.02 -0.01 -0.01 0.04 0.03 – 0.13 0.04 0.01 0.03 1 1 – 1 5 16 6 HD130948 -0.08 – +0.11 -0.10 -0.28 -0.11 -0.14 0.04 – 0.06 0.16 0.08 0.02 0.04 1 – 1 1 3 15 3 HD135145 -0.19 – – -0.11 +0.00 -0.03 +0.03 0.04 – – 0.16 0.06 0.02 0.03 1 – – 1 4 15 6 Chemical abundances in a sample of solar analogues 7 Table 4–continued Star [Mg/H] [Al/H] [Si/H] [Ca/H] [Ti/H] [Fe/H] [Ni/H] HD135633 +0.02 +0.14 +0.29 +0.33 +0.14 +0.23 +0.13 0.06 0.04 0.08 0.19 0.06 0.01 0.04 1 1 1 1 4 15 5 HD140385 +0.01 -0.03 -0.11 -0.28 +0.12 -0.24 -0.15 0.05 0.04 0.04 0.15 0.05 0.01 0.03 1 1 2 1 5 16 6 HD145404 -0.25 -0.25 – -0.23 -0.08 -0.18 -0.19 0.04 0.04 – 0.16 0.05 0.01 0.04 1 1 – 1 5 16 6 HD152264 -0.11 +0.00 +0.03 +0.16 +0.17 +0.07 +0.10 0.04 0.04 0.04 0.16 0.06 0.01 0.03 1 1 2 1 4 17 5 BD+292963 -0.17 -0.16 -0.28 -0.30 -0.08 -0.22 -0.23 0.04 0.04 0.04 0.13 0.04 0.01 0.04 1 1 1 1 5 17 5 HD156968 +0.00 -0.11 – -0.03 +0.06 -0.03 -0.02 0.05 0.04 – 0.16 0.06 0.02 0.04 1 1 – 1 5 16 6 HD168874 +0.00 +0.03 +0.05 +0.00 +0.04 -0.01 +0.07 0.05 0.04 0.08 0.16 0.06 0.02 0.04 1 1 1 1 5 15 4 BD+283198 +0.44 +0.30 +0.35 +0.46 +0.33 +0.27 +0.36 0.04 0.04 0.04 0.12 0.04 0.01 0.03 1 1 2 1 4 18 5 HD333565 -0.19 -0.05 -0.02 -0.16 +0.12 -0.03 +0.04 0.04 0.04 0.03 0.15 0.06 0.01 0.04 1 1 1 1 4 13 3 HD193664 -0.26 – +0.09 -0.02 -0.17 -0.12 -0.06 0.05 – 0.08 0.17 0.09 0.02 0.04 1 – 1 1 3 16 5 BD+473218 +0.06 +0.09 +0.15 +0.28 +0.24 +0.13 +0.32 0.04 0.04 0.04 0.16 0.06 0.01 0.03 1 1 2 1 4 15 5 HD210460 -0.49 – – -0.54 -0.38 -0.37 -0.37 0.05 – – 0.17 0.06 0.02 0.04 1 – – 1 4 13 5 TYC3986-3381-1 – +0.38 +0.48 +0.40 +0.29 +0.32 +0.23 – 0.05 0.04 0.15 0.07 0.01 0.04 0 1 1 1 4 14 4 HD212809 +0.01 – – +0.28 +0.03 +0.08 +0.08 0.07 – – 0.15 0.05 0.01 0.04 1 – – 1 4 15 5 BD+284515 +0.02 – +0.38 +0.24 -0.10 +0.07 +0.10 0.04 – 0.05 0.13 0.05 0.01 0.03 1 – 1 1 4 17 6 ertheless,thispatternisalsopresentinthecomparisonsam- Thisdiscrepancyisaslargeasthetypicaldispersionamong ple. catalogues included in Hinkelet al. (2014). As an example, The errors in theCa abundanceare, on average, larger in Fig. 3, we show thecomparison of our [Fe/H] values and those of Hypatia for the the stars HD 41708, HD 42807, thanfortheotherelementsandalwayshigherthan0.10dex. HD 111513, HD 129357, HD 140385, and HD 156968; we This anomaly is due to fact that the Ca abundance is very sensitivetotheerrorinsurfacegravity:infact,wefoundthat also include the iron abundance of Mahdi et al. (2016) for HD 42807 and HD 111513. If we take into account that σ =0.20dexproducesadifferenceof0.08dexintheCa logg the solar scale of Lodders et al. (2009), used as reference abundance, while for the other elements the uncertainty in logg does not affect muchthe overall error. byHinkel et al.(2014),hasaironabundance0.05dexlower than in Grevesse & Sauval (1998), the agreement with our Wefound8ofourstarsintheHypatiacatalogue,acom- results improves. pilation of chemical abundances from high-resolution spec- troscopy(Hinkelet al.2014),and2objectsarealso present Mahdi et al.(2016)providetheabundanceofSi,Ca,Ti, in the more recent work by Mahdi et al. (2016). We found Fe,andNiforthestarsHD42807andHD111513.Wefound a maximum (minimum) difference of +0.20 dex (-0.02 dex) a difference with our results between +0.08 and +0.11 dex between our abundances and those of Hinkel et al. (2014). for HD 42807 and in the interval −0.15 to +0.07 dex for 8 L´opez-Valdivia R., Bertone E. & Ch´avez M. 0.2 1.1 0.1 0.9 et s x) off Fe/H](deLiterature −00..01 malizedflux+00..57 [ or n −0.2 0.3 Hinkel et al. 2014 Mahdi et al. 2016 −0.3 0.1 −0.3 −0.2 −0.1 0.0 0.1 0.2 6695 6705 6715 6725 [Fe/H]TW (dex) wavelength(A˚) Figure 3. Comparison of our iron abundances and those of Figure 4. The spectra of TYC 2655-3677-1 (gray), and Hinkeletal.(2014)(filledcircles)andMahdietal.(2016)(filled HD 268356 (light gray), compared with the spectrum of Vesta squares). The empty circles represent the transformation of our (black). ironabundances totheHinkeletal.(2014)referencesolarabun- dances. Table 6.Probabilityofhosting agiant planet using[Fe/H] and the[Ref]index. Table 5.Solarabundances fromVestaspectrum andthe values ofGrevesse&Sauval (1998). Object [Fe/H] P(%) [Ref] P(%) HD5649 -0.32 0 – – Element Vesta G&S BD+60402 +0.19 7 +0.19 8 Mg 7.54±0.02 7.58±0.05 HD16894 +0.04 3 +0.07 3 Al 6.46±0.02 6.47±0.07 BD+60600 +0.35 15 +0.42 39 Si 7.52±0.02 7.55±0.05 HD232824 -0.09 1 -0.07 1 Ca 6.38±0.09 6.36±0.02 HD237200 +0.18 6 +0.15 6 Ti 4.98±0.03 5.02±0.06 HD26710 +0.08 4 +0.04 2 Fe 7.49±0.01 7.50±0.05 HD31867 -0.07 2 -0.03 1 Ni 6.23±0.02 6.25±0.04 HD33866 -0.22 1 – – HD41708 +0.08 4 – – HD42807 -0.10 1 -0.03 1 HD77730 -0.40 0 -0.33 0 HD 111513. Such values, although larger than our errors, HD110882 -0.37 0 – – canbeexplainedbysystematicdifferences,suchasdifferent HD110884 -0.14 1 – – loggf values or different atmospheric parameters adopted. HD111513 +0.04 3 +0.14 5 HD111540 +0.13 5 +0.15 6 HD124019 -0.05 2 +0.06 3 HD126991 -0.53 0 -0.43 0 4.3 Stars with broad line profiles HD129357 -0.01 2 +0.09 4 HD130948 -0.11 1 -0.03 1 Twostars,TYC2655-3677-1andHD228356,showlinepro- HD135145 -0.03 2 – – fileswhicharesignificantlybroaderthattherestofthesam- HD135633 +0.23 8 +0.21 9 ple (see Fig. 4). This is due to relatively high rotational HD140385 -0.24 0 -0.13 0 velocity (with a possible significant contribution by macro- HD145404 -0.18 1 – – turbulence).Thesetwoobjectsalsohavehighlithiumabun- HD152264 +0.07 4 +0.02 2 dance (A(Li)=2.54 for TYC 2655-3677-1 and HD 228653 BD+292963 -0.22 1 -0.22 0 of A(Li)=2.71; L´opez-Valdiviaet al. 2015), indicating that HD156968 -0.03 2 – – they are probably youngstars. HD168874 -0.01 2 +0.01 2 BD+283198 +0.27 10 +0.34 22 Their line profiles, however, are broad enough to make HD333565 -0.03 2 -0.06 1 verydifficulttoidentifyisolated, un-blendedlinesforacor- HD193664 -0.12 1 -0.08 1 rect abundance measurement. We have therefore excluded BD+473218 +0.13 5 +0.12 5 thetwostarsfromourabundanceanalysis.Wemeasuredthe HD210460 -0.37 0 – – FWHM and we computed, using eq. 6 of Strassmeier et al. TYC3986-3381-1 +0.32 13 – – (1990), theprojected rotation velocity (vsini) for 6 atomic HD212809 +0.08 4 – – lines in theregion around 6710 ˚A. BD+284515 +0.07 4 +0.17 7 We assumed a macroturbulence velocity of 3 kms−1 and an instrumental FWHM = 0.19 ˚A and we obtained vsini = 8.5 and 9.7 kms−1 for TYC 2655-3677-1 and HD 228653, respectively. Chemical abundances in a sample of solar analogues 9 1.0 1.0 0.5 0.5 Mg/Fe] 0.0 Al/Fe] 0.0 [ [ −0.5 −0.5 −11..00 −11..00 [Fe/H] [Fe/H] 0.5 0.5 e] e] Si/F 0.0 Ca/F 0.0 [ [ −0.5 −0.5 −11..00 −11..00 [Fe/H] [Fe/H] 0.5 0.5 e] e] F 0.0 F 0.0 Ti/ Ni/ [ [ −0.5 −0.5 −1.0 −1.0 −0.6 −0.4 −0.2 0.0 0.2 0.4 −0.6 −0.4 −0.2 0.0 0.2 0.4 [Fe/H] [Fe/H] Figure5.[X/Fe]vs[Fe/H]ratioforoursample(blackcircles),Neves etal.(2009)(graytriangles),Adibekyanetal.(2012)(graystars), andforHinkeletal.(2014)(graycircles).Theverticaldashedlineindicatesthesupermetallicitythreshold. ACKNOWLEDGEMENTS REFERENCES Adibekyan,V. Z., Sousa, S. G., Santos, N.C., et al. 2012, A&A,545, A32 ThisresearchhasmadeuseoftheSIMBADdatabase,oper- Alibert, Y., Mordasini, C., & Benz, W. 2004, A&A, 417, atedatCDS,Strasbourg,France.Theauthorswouldliketo L25 thank CONACyTfor financial support through grants CB- Bush, T. C., & Hintz, E. G. 2008, AJ, 136, 1061 2011-169554 and CB-2015-256961. 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