J/ApJ/687/471ivo://CDS.VizieR/J/ApJ/687/471doi:10.26093/cds/vizier.16870471CDSBerghea C.T.Weaver K.A.Colbert E.J.M.Roberts T.P.2018-02-12T08:45:34Z2011-01-12T13:38:22ZCDS support team

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

cds-question@unistra.frgalaxiesx-ray-sourcesastronomical-object-identificationTo test the idea that ultraluminous X-ray sources (ULXs) in external galaxies represent a class of accreting intermediate-mass black holes (IMBHs), we have undertaken a program to identify ULXs and a lower luminosity X-ray comparison sample with the highest quality data in the Chandra archive. We establish as a general property of ULXs that the most X-ray-luminous objects possess the flattest X-ray spectra (in the Chandra bandpass). No prior sample studies have established the general hardening of ULX spectra with luminosity. This hardening occurs at the highest luminosities (absorbed luminosity >=5x10^39^erg/s) and is in line with recent models arguing that ULXs are actually stellar mass black holes. From spectral modeling, we show that the evidence originally taken to mean that ULXs are IMBHs - i.e., the "simple IMBH model" - is nowhere near as compelling when a large sample of ULXs is looked at properly. During the last couple of years, XMM-Newton spectroscopy of ULXs has to a large extent begun to negate the simple IMBH model based on fewer objects. We confirm and expand these results, which validates the XMM-Newton work in a broader sense with independent X-ray data.2008ApJ...687..471Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/687/471CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/chandra : The Chandra Archive Log (CXC, 1999-)VII/145 : Nearby Galaxies Catalogue (NBG) (Tully 1988)J/ApJ/664/458 : Spectral fit of ULX sources (Devi+, 2007)J/ApJ/649/730 : ULX population in nearby galaxies from XMM (Winter+, 2006)J/A+A/429/1125 : Catalog of Ultraluminous X-ray sources (Liu+, 2005)J/ApJS/154/519 : Properties of ultraluminous X-ray candidates (Swartz+, 2004)J/MNRAS/344/134 : Chandra ultraluminous X-ray sources (Humphrey+, 2003)J/ApJS/143/25 : Intermediate-luminosity X-ray objects catalog (Colbert+,https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/687/471https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/687/471http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/687/471https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/687/471https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/687/471http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/687/471GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/687/471/table2 (Properties of sample objects)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/687/471/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/687/471/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/687/471/table2?GETtext/xml+votable180.050000true21.1466673.7919440.0055555555555555566/2155 2409 2709 3506 5995 6034 6040 7225 7606 7743 8225 10761 10841 10856 10905 10911 11127 11263 11434 15593 16655 17754 18212 25344 27765 27914 28141 28184 28496 33193 35512 41586 43233 43262 43881 46491https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/687/471?format=asciiX-raydefaultJ/ApJ/687/471/table2Properties of sample objectsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintS[S /SC] S for ULX sample or SC for comparison samplemeta.idcharSeqRunning sequence number (<[BWC2008] {S|SC} NN> in Simbad)meta.id;meta.mainintNameObject name (<[BWC2008] {U|CNN}> in Simbad)meta.idcharRAJ2000X-ray hour of right ascension (J2000)pos.eq.ra;meta.mainDEJ2000X-ray degree of declination (J2000)pos.eq.dec;meta.mainGalaxyHost galaxy namemeta.id.parentcharDist? Galaxy distance from Tully (1988, Cat. VII/145)Mpcpos.distance;pos.heliocentricfloatnullableNHgalGalactic Hydrogen absorption column density1e+20cm**-2physfloatObsIDObservation IDmeta.id;obsintCCDCCD number where the object is located and subarray values (in parentheses) (1)instr.saturationcharlogLxApproximate observed luminosity in the energy band 0.3-8.0keV (2)log(1e-07W)phys.luminosity;em.X-rayfloatDateDate of observation starttime.epochnullableExpExposure timekstime.duration;obs.exposurefloatCtsNet counts in the 0.3-8.0keV energy bandctphot.count;em.X-raydoublethetaOff-axis angle of the source (3)arcminpos.posAngfloate_ThetaTheta uncertaintyarcminstat.error;pos.posAngfloatONameX-ray common names from the literature (4)meta.id.crosscharLocLocation in the galaxy (5)meta.codecharr_ONameReferences (see refs.dat file) (4)meta.ref;pos.framecharJ/ApJ/687/471/refsReferencesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRefReference numbermeta.id;meta.mainintBibCodeBibcodemeta.bib.bibcodecharAutAuthor(s) namemeta.bib.authorchar