J/A+A/534/A123ivo://CDS.VizieR/J/A+A/534/A123doi:10.26093/cds/vizier.35340123CDSGratton R.G.Lucatello S.Carretta E.Bragaglia A.D'Orazi V.,Al Momany Y.2017-12-18T07:56:51Z2012-03-13T13:43:59ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frglobular-star-clustershorizontal-branch-starsspectroscopyGlobular clusters have been recognized to host multiple stellar populations. A spectacular example of this is the massive cluster NGC 2808, where multiple populations have been found along the horizontal branch (HB) and the main sequence (MS). Studies of red giants showed that this cluster appears homogeneous insofar Fe abundance is concerned, but it shows an extended anticorrelation between Na and O abundances. The Na-poor, O-rich population can be identified with the red MS, and the Na-rich, O-poor one with the blue one. This may be understood in terms of different He content, He being correlated with Na. A prediction of this scenario is that He-rich, Na-rich He-core burning stars, because they are less massive, will end up on the bluer part of the HB, while He-poor, Na-poor stars will reside on the red HB. The aim of this paper is to verify this prediction. To this purpose, we acquired high-resolution spectra of regions including strong O and Na lines in several tens of HB stars of NGC 2808, sampling both the red and blue parts of the HB.2011A&A...534A.123Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/534/A123CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/391/945 : HST photometry of 74 galactic globular clusters (Piotto+, 2002)J/A+A/549/A41 : Horizontal branch stars in 47 Tuc and M5 (Gratton+, 2013)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/534/A123https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/534/A123http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/534/A123https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/534/A123https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/534/A123http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/534/A123GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/534/A123/table1 (Basic data for program stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/534/A123/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/534/A123/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/534/A123/table1?GETtext/xml+votable180.050000true137.95762917-64.826636110.0055555555555555566/37291 37294 37633 376368.650015785639275e-20 9.710690472292815e-20https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/534/A123?format=asciiOpticaldefaultJ/A+A/534/A123/table1Basic data for program starsBmagB magnitudemagphot.mag;em.opt.BfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTypeType of source (Blue HB, Red HB or Lower RGB)src.classcharStarStar identification number, <Cl* NGC 2808 PKD NNNNN> in Simbadmeta.id;meta.mainintprimaryn_StarSimbad column added by the CDSmeta.ref.urlcharRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainVmagV magnitudemagphot.mag;em.opt.VfloatKmag? 2MASS Ks magnitudemagphot.mag;em.IR.KfloatnullableRV? Radial velocitykm/sphys.veloc;pos.heliocentricfloatnullableS/N1? HR12 grating signal-to-noise ratiostat.snrfloatnullableS/N2? HR19 grating signal-to-noise ratiostat.snrfloatnullableNoteMembership notemeta.notecharJ/A+A/534/A123/table2Atmospheric parameters and abundancesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTypeType of source (Blue HB, Ref HB or Lower RGB)src.classcharStarStar identification numbermeta.id;meta.mainintTeffEffective temperatureKphys.temperature.effectiveintloggSurface gravitylog(cm.s**-2)phys.gravityfloato_[FeI/H]? Number of lines for [FeI/H]meta.numberintnullable[FeI/H]? Abundance [FeI/H]log(Sun)phys.abundfloatnullablee_[FeI/H]? rms uncertainty on [FeI/H]log(Sun)stat.error;phys.abundfloatnullable[FeII/H]? Abundance [FeII/H]log(Sun)phys.abundfloatnullableo_[O/Fe]? Number of lines for [O/Fe]meta.numberintnullable[O/Fe]? Abundance [OI/Fe]log(Sun)phys.abundfloatnullablee_[O/Fe]? rms uncertainty on [O/Fe]log(Sun)stat.error;phys.abundfloatnullableo_[Na/Fe]Number of lines for [Na/Fe]meta.numberint[Na/Fe]Abundance [NaI/Fe]log(Sun)phys.abundfloate_[Na/Fe]? rms uncertainty on [Na/Fe]log(Sun)stat.error;phys.abundfloatnullable[Mg/Fe]? Abundance [MgI/Fe]log(Sun)phys.abundfloatnullable[Si/Fe]? Abundance [SiI/Fe]log(Sun)phys.abundfloatnullable[Ca/Fe]? Abundance [CaI/Fe]log(Sun)phys.abundfloatnullable[Ba/Fe]? Abundance [BaII/Fe]log(Sun)phys.abundfloatnullable