J/ApJ/687/1019ivo://CDS.VizieR/J/ApJ/687/1019doi:10.26093/cds/vizier.16871019CDSElsner R.F.Heinke C.O.Cohn H.N.Lugger P.M.Maxwell J.E.,Stairs I.H.Ransom S.M.Hessels J.W.T.Becker W.Huang R.H.H.,Edmonds P.D.Grindlay J.E.Bogdanov S.Ghosh K.Weisskopf M.C.2017-07-12T06:59:49Z2011-01-12T14:17:40ZCDS support team

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

cds-question@unistra.frglobular-star-clustersx-ray-sourcesastronomical-object-identificationWe observe the nearby, low-density globular cluster M71 (NGC 6838) with the Chandra X-Ray Observatory to study its faint X-ray populations. Five X-ray sources are found inside the cluster core radius, including the known eclipsing binary millisecond pulsar (MSP) PSR J1953+1846A. The X-ray light curve of the source coincident with this MSP shows marginal evidence for periodicity at the binary period of 4.2hr. Its hard X-ray spectrum and luminosity resemble those of other eclipsing binary MSPs in 47 Tuc, suggesting a similar shock origin of the X-ray emission. A further 24 X-ray sources are found within the half-mass radius, reaching to a limiting luminosity of 1.5x10^30^ergs/s (0.3-8keV). From a radial distribution analysis, we find that 18+/-6 of these 29 sources are associated with M71, somewhat more than predicted, and that 11+/-6 are background sources, both Galactic and extragalactic. M71 appears to have more X-ray sources in the range L_X_=10^30^-10^31^ergs/s than expected by extrapolating from other studied clusters using either mass or collision frequency. We explore the spectra and variability of these sources and describe the results of ground-based optical counterpart searches.2008ApJ...687.1019Ehttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/687/1019CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/284 : The USNO-B1.0 Catalog (Monet+ 2003)II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)I/259 : The Tycho-2 Catalogue (Hog+ 2000)B/chandra : The Chandra Archive Log (CXC, 1999-)J/A+AS/144/227 : BV photometry of M71 (Geffert+, 2000)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/687/1019https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/687/1019http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/687/1019https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/687/1019https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/687/1019http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/687/1019GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/687/1019/Xsources (Combined table from original tables)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/687/1019/Xsources?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/687/1019/Xsources?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/687/1019/Xsources?GETtext/xml+votable180.050000true298.4226291718.785902780.0055555555555555566/129431.398457827073138e-19 4.067783865629509e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/687/1019?format=asciiX-raydefaultJ/ApJ/687/1019/XsourcesCombined table from original tablesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintrlHalf-mass radius (r_h_) limits (1)meta.codecharIDSource identification (<[EHC2008] [s/i]sNN> in Simbad)meta.id;meta.maincharf_ID[j] Flag for s55 (in table 1) (2)meta.codecharreRadius of the detect cell for collecting X-ray countsarcsecphys.angSizefloatCxNumber of 0.3-8.0keV source counts collected in the detect cellphot.count;em.X-rayfloatSigXRadius enclosing the true source position with 68% confidence (3)arcsecstat.fit.paramfloatChipCCD on which the X-ray source appears (only for table 2) (4)arcminpos.cartesian.x;instr.detcharrM71? Radius from the nominal center of the cluster (J19:53:46.1+18:46:42; only for table 1)arcminphys.angSizefloatnullableoff? Radial offset of candidate counterparts (5)arcsecpos.angDistancefloatnullableJmag? J magnitude of a candidate counterpart found in the 2MASS catalog (5)magphot.mag;em.IR.JfloatnullableR1mag? R1 magnitude of a candidate counterpart found in the USNO-B1.0 catalog (5)magphot.mag;em.opt.RfloatnullableR2mag? R2 magnitude of a candidate counterpart found in the USNO-B1.0 catalog (5)magphot.mag;em.opt.RfloatnullableVmag? VT magnitude of a candidate counterpart found in the Tycho-2 catalog (5)magphot.mag;em.opt.VfloatnullableProb? Probability of chance coincidence (5)(6)%statfloatnullableComComment (counterpart or location)meta.notechar2MDisplay the 2MASS data (Cutri et al. 2003, Cat. II/246)meta.ref.urlcharUSNODisplay the USNO-B1.0 data (Monet et al. 2003, Cat. I/284)meta.ref.urlcharTYC2Display the Tycho-2 data (Hog et al. 2000, Cat. I/259)meta.ref.urlcharRAJ2000Hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of declination (J2000)pos.eq.dec;meta.main