J/PASP/106/486ivo://CDS.VizieR/J/PASP/106/486doi:10.26093/cds/vizier.61060486CDSAnthony-Twarog B.J.Twarog B.A.Sheeran M.2025-09-09T14:11:50Z1997-12-09T21:45:16ZCDS support team

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

cds-question@unistra.fropen-star-clustersccd-photometryA CCD study of the peculiar open cluster, Melotte 66, on the vbyHbeta system is presented. The V,(b-y) color-magnitude diagram of this metal-deficient, old disk cluster confirms the anomalous features found in photographic BV studies and extends the main sequence to V=20. The main sequence exhibits a (b-y) color range significantly larger than expected from photometric errors alone; the (b-y) colors are correlated with Hbeta implying that the dispersion is real and is not the result of variable reddening across the cluster. The m1 indices for the turnoff stars imply a spread in [Fe/H] too small to explain the color range. Though the subgiant region is poorly defined, the region above the turnoff in the Hertzsprung gap is richly populated by a group of "yellow stragglers" whose membership is confirmed by radial star counts and radial velocities. The giant branch is richly populated but shows a smaller spread in color at a given V than one would expect from the turnoff region. More important, the giants exhibit a large scatter in m1, in contradiction with the turnoff observations. Various explanations for these observations are discussed, including CN variations among the giants triggered by either binary evolution or rapid rotation among the main-sequence stars.1994PASP..106..486Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/PASP/106/486CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/MNRAS/174/471 : Melotte 66 (Hawarden+, 1976)J/A+A/283/911 : Abundances in NGC 2243 and Mel 66 (Gratton+ 1994)J/A+A/488/943 : Abundances of giants in four Galactic clusters (Sestito+ 2008)J/A+A/566/A39 : UBVI photometry of Melotte 66 (Carraro+, 2014)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/PASP/106/486https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/PASP/106/486http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/PASP/106/486https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/PASP/106/486https://vizier.iucaa.in/viz-bin/votable?-source=J/PASP/106/486http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/PASP/106/486GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/PASP/106/486/table3 (Photometric indices for Mel 66 stars)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/PASP/106/486/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/PASP/106/486/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/PASP/106/486/table3?GETtext/xml+votable180.050000true111.65357028-47.625197220.0055555555555555566/39129 391313.322582951404819e-19 3.852589004194616e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/PASP/106/486?format=asciidefaultJ/PASP/106/486/table3Photometric indices for Mel 66 starsNy[2/16] Number of y framesmeta.numberintHbeta? H{beta} indexspect.indexfloatnullableNb[1/17] Number of b framesmeta.numberintNv[2/16] Number of v framesmeta.numberinte_Hbeta? rms uncertainty on Hbeta indexstat.error;spect.linefloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHaw? Hawarden identification number (1)meta.idintnullableID[1/1458] Identification numbermeta.id;meta.mainintXposX positionpixpos.cartesian.x;instr.detfloatYposY positionpixpos.cartesian.y;instr.detfloatVmag[11/18] V magnitude (apparent)magphot.mag;em.opt.Vfloate_Vmagrms uncertainty on V magnitudemagstat.error;phot.magfloatb-y(b-y) colormagphot.color;em.opt.B;em.opt.Vfloate_b-yrms uncertainty on (b-y) colormagstat.error;phot.color;em.opt.Bfloatm1m_1_ indexmagphot.colorfloate_m1rms uncertainty on m1 indexmagstat.errorfloatNw[0/20] Number of H{beta} wide framesmeta.numberintNn[0/11] Number of H{beta} narrow framesmeta.numberint_RAPosition computed from a comparison with 2MASS (II/246) ({sigma}=0.1'') (right ascension part)degpos.eq.ra;meta.main_DEPosition computed from a comparison with 2MASS (II/246) ({sigma}=0.1'') (declination part)degpos.eq.dec;meta.main