J/ApJS/156/35ivo://CDS.VizieR/J/ApJS/156/35doi:10.26093/cds/vizier.21560035CDSEckart M.E.Laird E.S.Stern D.Mao P.H.Helfand D.J.Harrison F.A.2008-02-09T14:37:09Z2008-02-09T15:35:59ZCDS support team

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

cds-question@unistra.frsurveysx-ray-sourcesphotometryThe Serendipitous Extragalactic X-ray Source Identification (SEXSI) Program is designed to expand significantly the sample of identified extragalactic hard X-ray sources at intermediate fluxes, 10^-13^ergs/cm^2^/s<~S_2-10keV_<10^-15^ergs/cm^2^/s. SEXSI, which includes sources derived from more than 2{deg}^2^ of Chandra images, provides the largest hard X-ray-selected sample yet studied, offering an essential complement to the Chandra Deep Fields (total area 0.2{deg}^2^). In this paper we describe R-band optical imaging of the SEXSI fields from the Palomar, MDM, and Keck observatories. We have identified counterparts or derived flux limits for nearly 1000 hard X-ray sources. Using the optical images, we derive accurate source positions. We investigate correlations between optical and X-ray flux, and optical flux and X-ray hardness ratio. We also study the density of optical sources surrounding X-ray counterparts, as well as the properties of optically faint, hard X-ray sources.2005ApJS..156...35Ehttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/156/35CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/chandra : The Chandra Archive Log (CXC, 2002)J/AJ/122/2810 : Chandra Deep Field North Survey. 1Ms catalog (Brandt+, 2001)J/AJ/126/539 : Chandra Deep Fields North & South. 2Ms Cat. (Alexander+, 2003)J/ApJS/139/369 : Chandra Deep Field South. 1Ms catalog (Giacconi+, 2002)J/ApJ/596/944 : SEXSI catalog (Harrison+, 2003)J/ApJS/165/19 : SEXSI catalog. III (Eckart+, 2006)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/156/35https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/156/35http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/156/35https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/156/35https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/156/35http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/156/35GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJS/156/35/table3 (Optical follow-up source catalog)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/156/35/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/156/35/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/156/35/table3?GETtext/xml+votable180.050000true35.42812542.44819440.0055555555555555566/13 24 1128 1129 2388 2389 2390 2409 2411 3389 6495 7178 7273 8268 9272 10037 10080 10338 10344 10345 10386 10387 10583 10589 10743 10761 10888 11460 11461 11605 11632 11634 11791 11802 16276 18780 18782 18878 19220 22959 22970 25769 28479 49125 49127https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJS/156/35?format=asciiX-rayOpticaldefaultJ/ApJS/156/35/table3Optical follow-up source catalogrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCXOSEXSIIAU-registered name (JHHMMSS.s+DDMMSS)meta.id;meta.maincharRAJ2000Hour of Right Ascension (J2000) (1)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000) (1)pos.eq.dec;meta.mainOAAOff-axis anglearcmininstr.offsetfloatHFluxUnabsorbed hard band (2.0-10keV) flux in units of 10^-15^erg/cm^2^/s1e-18W.m**-2phot.flux;em.X-raydoubleHS/NSignal-to-noise ratio of the hard detectionstat.snrfloatHRHardness ratio (2)phot.flux;arith.ratiofloatl_HR[0,1] Hardness ratio limit flag (3)meta.code.errorintCl[0,1] Cluster flag (4)meta.noteintOID[0,6] Optical ID flag (5)meta.noteintRcmag? The Cousins R Magnitudemagphot.mag;em.opt.Rfloatnullablee_Rcmag? Error on Rcmagmagstat.error;phot.mag;em.opt.RfloatnullableRclim? Limiting Rcmag of Imagemagphot.magfloatnullablef_Rcmag[0,1]? Flag on Rcmag (6)meta.codeintnullableoRA? Optical counterpart RA offset from X-ray RAarcsecpos.eq.ra;arith.difffloatnullableoDE? Optical counterpart DE offset from X-ray DEarcsecpos.eq.dec;arith.difffloatnullabledPos? Position difference of optical counterpart and X-ray sourcearcsecpos.angDistancefloatnullableFx/Fo? Log of the HFlux/RFlux ratiophot.flux;arith.ratiofloatnullableStell? SExtractor stellarity fraction (7)src.class.starGalaxyfloatnullablePapIDisplay the results from Paper I (2003, Cat. J/ApJ/596/944)meta.ref.urlchar