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Abundance difference between components of wide binaries. II. The southern sample
Aims.We present high-precision iron abundance differences for 33 widebinaries with similar components. They were observed with the FEROSspectrograph at ESO, looking for abundance anomalies due to theingestion of metal rich material of a planetary origin. Methods:.An optimized data analysis technique and the high quality of thespectra allowed us to achieve an error of about 0.02 dex for pairs withsmall temperaure differences. Results: . We found one case (HIP64030 = HD 113984) with a large (0.27 dex) abundance difference. Theprimary of this binary appears to be a blue straggler, and the abundancedifference might be due to the peculiar evolution of the star. A fewother pairs show small abundance differences (≤0.09 dex). In a fewcases these differences suggest the ingestion of a small amount of metalrich material, but in others they are likely spurious, because of thelarge temperature difference, high level of magnetic activity, ordifferent evolutionary phases between the components. Some cases ofabundance differences involving pairs with warm (Teff ≥6000 K) primaries might be due to the diffusion of heavy elements;dedicated theoretical models for the stellar parameters of the targetswould be welcome. Conclusions: . This study confirms ourpreliminary result based on analysis of 23 pairs (Desidera et al. 2004)that the occurrence of large alterations in stellar abundances caused bythe ingestion of metal rich, rocky material is not a common event. Forat least 65% of the pairs with components warmer than 5500 K, the limitson the amount of rocky material accreted by the program stars arecomparable to the estimates of rocky material accreted by the Sun duringits main-sequence lifetime.
| Spectroscopic characterization of a sample of southern visual binaries
Aims.We present the spectroscopic characterization of 56 pairs of visualbinaries with similar components, based on high resolution spectraacquired with FEROS at ESO La Silla. Methods: .For all stars, wemeasured radial and rotational velocities and CaII H&K emission. Results: .Five previously unknown double lined spectroscopic binarieswere found. Six other pairs show velocity differences that are notcompatible with the orbital motion of the wide pair, indicating thepresence of further companion(s) in the system. The fraction of visualbinaries that contain additional spectroscopic components is27±10%, compatible with other literature estimates. The ages ofthe components of the pairs derived from chromospheric activitytypically show apparent differences of about 0.2 dex. A few pairs show arather large difference in activity level, but in most cases this isconsistent with the variability of chromospheric emission observed forthe Sun along its magnetic cycle.
| Abundance difference between components of wide binaries
We present iron abundance analysis for 23 wide binaries with mainsequence components in the temperture range 4900-6300 K, taken from thesample of the pairs currently included in the radial velocity planetsearch on going at the Telescopio Nazionale Galileo (TNG) using the highresolution spectrograph SARG. The use of a line-by-line differentialanalysis technique between the components of each pair allows us toreach errors of about 0.02 dex in the iron content difference. Most ofthe pairs have abundance differences lower than 0.02 dex and there areno pairs with differences larger than 0.07 dex. The four cases ofdifferences larger than 0.02 dex may be spurious because of the largererror bars affecting pairs with large temperature difference, cold starsand rotating stars. The pair HD 219542, previously reported by us tohave a different composition, here is shown to be normal. Fornon-rotating stars warmer than 5500 K, characterized by a thinnerconvective envelope and for which our analyis appears to be of higheraccuracy, we are able to exclude in most cases the consumption of morethan 1 Earth Mass of iron (about 5 Earth masses of meteoritic material)during the main sequence lifetime of the stars, placing more stringentlimits (about 0.4 Earth masses of iron) in five cases of warm stars.This latter limit is similar to the estimates of rocky material accretedby the Sun during its main sequence lifetime. Combining the results ofthe present analysis with those for the Hyades and Pleiades, we concludethat the hypothesis that pollution by planetary material is the onlymechanism responsible for the highest metallicity of the stars withplanets may be rejected at more than 99% level of confidence if theincidence of planets in these samples is as high as 8% and similar tothe field stars included in current radial velocity surveys. However,the significance of this result drops considerably if the incidence ofplanets around stars in binary systems and clusters is less than a halfof that around normal field stars.Based on observations made with the Italian Telescopio Nazionale Galileo(TNG) operated on the island of La Palma by the Centro Galileo Galileiof the INAF (Istituto Nazionale di Astrofisica) at the SpanishObservatorio del Roque de los Muchachos of the Instituto de Astrofisicade Canarias.The equivalent widths are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/420/683
| Photographic measures of double stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....1..357T&db_key=AST
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