J/ApJ/837/130ivo://CDS.VizieR/J/ApJ/837/130doi:10.26093/cds/vizier.18370130CDSVats S.van den Berg M.2021-01-25T08:39:04Z2017-11-23T12:18:34ZCDS support team

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

cds-question@unistra.fropen-star-clustersx-ray-sourcesvisible-astronomybroad-band-photometryastronomical-object-identificationx-ray-binary-starscataclysmic-variable-starsWe present the first X-ray study of Collinder 261 (Cr261), which at an age of 7Gyr is one of the oldest open clusters known in the Galaxy. Our observation with the Chandra X-Ray Observatory is aimed at uncovering the close interacting binaries in Cr261, and reaches a limiting X-ray luminosity of L_X_~4x10^29^erg/s (0.3-7keV) for stars in the cluster. We detect 107 sources within the cluster half-mass radius r_h_, and we estimate that among the sources with L_X_>~10^30^erg/s, ~26 are associated with the cluster. We identify a mix of active binaries and candidate active binaries, candidate cataclysmic variables, and stars that have "straggled" from the main locus of Cr261 in the color-magnitude diagram. Based on a deep optical source catalog of the field, we estimate that Cr261 has an approximate mass of 6500M_{sun}_, roughly the same as the old open cluster NGC6791. The X-ray emissivity of Cr261 is similar to that of other old open clusters, supporting the trend that they are more luminous in X-rays per unit mass than old populations of higher (globular clusters) and lower (the local neighborhood) stellar density. This implies that the dynamical destruction of binaries in the densest environments is not solely responsible for the observed differences in X-ray emissivity.2017ApJ...837..130Vhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/837/130CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/chandra : The Chandra Archive Log (CXC, 1999-2014)B/eso : ESO Science Archive Catalog (ESO, 1991-2016)I/284 : The USNO-B1.0 Catalog (Monet+ 2003)VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)I/317 : The PPMXL Catalog (Roeser+ 2010)J/A+A/418/509 : Chandra observation of M67 (Van Den Berg+, 2004)J/ApJ/635/214 : Chandra X-ray sources and NIR identifications (Ebisawa+, 2005)J/A+A/438/291 : X-ray sources in NGC 188 (Gondoin+, 2005)J/A+A/453/635 : Modelling the Galactic Interstellar Extinct. (Marshall+, 2006)J/AJ/135/2264 : Stellar radial velocities in NGC 188 (Geller+, 2008)J/A+A/490/113 : X-ray sources in NGC 752 (Giardino+, 2008)J/MNRAS/409/1281 : Old star clusters in the FSR catalogue (Froebrich+, 2010)J/A+A/548/A122 : Berkeley 39 stars photometry and abundances (Bragaglia+, 2012)J/A+A/558/A53 : MW global survey of star clusters. II. (Kharchenko+, 2013)J/AJ/146/43 : WIYN open cluster study. LV. NGC 6819 (Platais+, 2013)J/ApJ/770/98 : Chandra study of NGC 6791 (van den Berg+, 2013)J/ApJS/208/9 : Intrinsic colors and temperatures of PMS stars (Pecaut+, 2013)J/AJ/150/97 : RVs in M67. I. 1278 candidate members (Geller+, 2015)J/ApJS/224/40 : Catalog of Chandra ACIS point like sources (Wang+, 2016)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/837/130https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/837/130http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/837/130https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/837/130https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/837/130http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/837/130GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/837/130/table1 (Catalog of Chandra sources in Cr 261)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/837/130/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/837/130/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/837/130/table1?GETtext/xml+votable180.050000true189.59730111-68.368591110.0055555555555555566/41612 416133.322582951404819e-19 3.852589004194616e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/837/130?format=asciiX-rayOpticaldefaultJ/ApJ/837/130/table1Catalog of Chandra sources in Cr 261recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeq[1/151] Running sequence number (G1)meta.id;meta.mainintprimaryf_Seq[d] Flag on Seq (1)meta.codecharCXOUOfficial IAU identifier (HHMMSS.s+DDMMSS; J2000)meta.idcharRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainePos[0.3/8] The 95% confidence radius (2)arcsecphys.angSizefloattheta[0.2/11] Angular offset (3)arcminpos;arith.difffloatCT[3/473] The 0.3-7keV net counts extractedctphot.count;em.X-rayinte_CT[2/22] The 1{sigma} uncertainty in CTctstat.errorintl_CSLimit flag on CSmeta.code.errorcharCS[0/226] The 0.3-2keV net counts extractedctphot.count;em.X-rayfloate_CS[1/15]? The 1{sigma} uncertainty in CSctstat.errorintnullableFXu[0.5/100] Unabsorbed 0.3-7keV X-ray flux (4)1e-15mW.m**-2phot.flux;em.X-rayfloatE50[0.7/6] Median energykeVem.energyfloate_E50[0.06/2] The 1{sigma} uncertainty in E50keVstat.errorfloatMatchOptical counterpart match? (+ = present; - = absent; see table 2)meta.codecharW16Display data from Wang+, 2016, J/ApJS/224/40, within 1"meta.ref.urlintnullableSimbadSimbad column added by the CDSmeta.ref.urlcharJ/ApJ/837/130/table2Optical Counterpart PropertiesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeq[4/151] Sequence number (G1)meta.id;meta.mainintOIDOptical identifier (1)meta.id.crosscharf_OID[ac] Flag on OID (2)meta.codecharDox[0.05/8] Distance between X-ray and its optical counterpartarcsecpos.angDistancefloatVmag[11.4/23.8] Johnson V band magnitudemagphot.mag;em.opt.Vfloatf_Vmag[bd] Flag on Vmag (2)meta.codecharB-V[0.5/2.1]? The (B-V) color indexmagphot.color;em.opt.B;em.opt.Vfloatnullablef_B-V[de] Flag on B-V (2)meta.codecharVarMazur+ (1995MNRAS.273...59M) short-period binary identifier; <Cl* Collinder 261 MKK VNN> in Simbadmeta.id.crosscharPer[0.2/2.2]? Period of short-period binarydtime.perioddoublenullablef_Per[?] Uncertainty flag on Permeta.codecharVTypeMazur+ (1995MNRAS.273...59M) variable typesrc.classcharLXu[0.5/25.5] Unabsorbed 0.3-7keV X-ray luminosity (3)1e+23Wphys.luminosity;em.X-rayfloatlogR[-4.8/0.3] Log ratio of X-ray to V band fluxes (4)phot.flux;arith.ratiofloatClassClassification (5)src.classchar