J/ApJ/786/14ivo://CDS.VizieR/J/ApJ/786/14doi:10.26093/cds/vizier.17860014CDSMucciarelli A.Lovisi L.Lanzoni B.Ferraro F.R.2017-09-04T08:00:29Z2017-07-03T15:05:57ZCDS support team

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

cds-question@unistra.frglobular-star-clusterseffective-temperatureWe present the helium abundance of the two metal-poor clusters M30 and NGC 6397. Helium estimates have been obtained by using the high-resolution spectrograph FLAMES at the European Southern Observatory Very Large Telescope and by measuring the He I line at 4471 {AA} in 24 and 35 horizontal branch (HB) stars in M30 and NGC 6397, respectively. This sample represents the largest data set of He abundances collected so far in metal-poor clusters. The He mass fraction turns out to be Y=0.252+/-0.003 ({sigma}=0.021) for M30 and Y=0.241+/-0.004 ({sigma}=0.023) for NGC 6397. These values are fully compatible with the cosmological abundance, thus suggesting that the HB stars are not strongly enriched in He. The small spread of the Y distributions are compatible with those expected from the observed main sequence splitting. Finally, we find a hint of a weak anticorrelation between Y and [O/Fe] in NGC 6397 in agreement with the prediction that O-poor stars are formed by (He-enriched) gas polluted by the products of hot proton-capture reactions.2014ApJ...786...14Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/786/14CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/490/777 : Abundances of Population II stars in NGC 6397 (Lind+, 2008)J/A+A/505/L13 : Lithium in globular NGC 6397 (Gonzalez Hernandez+, 2009)J/AJ/142/63 : Abundance of five stars in NGC 6397 (Koch+, 2011)J/ApJ/754/91 : Abundances and velocities of NGC 6397 stars (Lovisi+, 2012)J/ApJ/772/148 : Blue straggler and red giant stars in M30 (Lovisi+, 2013)J/A+A/589/A61 : Stellar parameters and abundances for M30 (Gruyters+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/786/14https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/786/14http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/786/14https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/786/14https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/786/14http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/786/14GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/786/14/table1 (Stellar parameters and He abundances)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/786/14/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/786/14/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/786/14/table1?GETtext/xml+votable180.050000true325.0989565-23.16131420.0055555555555555566/42076 48434 48440https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/786/14?format=asciidefaultJ/ApJ/786/14/table1Stellar parameters and He abundancesSimbadNameSimbad column added by the CDSmeta.idcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGCGlobular cluster identifier (M30, NGC6397)meta.id.parentcharIDSource identifier ([LML2012] NNNNNNN for NGC6397 and [LML2013] NNNNNNNNN for M30 in Simbad) (1)meta.id;meta.mainintRAJ2000Right Ascension in decimal degrees (J2000) (1)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000) (1)degpos.eq.dec;meta.mainTeffEffective temperature (1)Kphys.temperature.effectiveintlog(g)Log of the surface gravity (1)log(cm.s**-2)phys.gravityfloatYHelium mass fractionphys.abund.Yfloate_YThe 1{sigma} uncertainty in Ystat.error;pos.cartesian.yfloat