J/AJ/96/1632ivo://CDS.VizieR/J/AJ/96/1632doi:10.26093/cds/vizier.50961632CDSSchade D.Vandenberg D.A.Hartwick F.D.A.1997-12-09T19:42:17Z1997-12-09T20:42:14ZCDS support team

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

cds-question@unistra.frglobular-star-clustersccd-photometryWe present new CCD photometry for the globular cluster M55 that extends well below the main-sequence turnoff. Combining these new data with previously published photographic photometry of cluster giants and horizontal-branch stars yields a high-quality composite color-magnitude diagram (CMD). A comparison of the latter with recent CMDs for M68 and NGC 6752-two clusters whose metallicities bracket that of M55-suggests (1) that the reddening to M55 may be as high as E(B-V)=0.14mag, and (2) that all three systems have similar ages. In particular, if the apparent distance modulus to M55 is (m-M)_V_=14.10mag, then isochrones for Y=0.24 and high [O/Fe] would suggest an age of ~14Gyr. Very encouraging agreement of the observations with theoretical predictions is found.1988AJ.....96.1632Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/96/1632CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/96/1632https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/96/1632http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/96/1632https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/96/1632https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/96/1632http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/96/1632GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/AJ/96/1632/table1CCD photometry in M 55VmagV magnitudemagphot.mag;em.opt.VfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStar[1/617]+ Star numbermeta.id;meta.mainintprimaryindexedXposX position (1)pixpos.cartesian.x;instr.detfloatYposY position (1)pixpos.cartesian.y;instr.detfloatB-VB-V colour indexmagphot.color;em.opt.B;em.opt.Vfloat