J/AJ/108/1350ivo://CDS.VizieR/J/AJ/108/1350doi:10.26093/cds/vizier.51081350CDSWhitney J.H.O'Connell R.W.Rood R.T.Dorman B.Landsman W.B.,Cheng K.-P.Bohlin R.C.Hintzen P.M.N.Roberts M.S.Smith A.M.,Smith E.P.Stecher T.P.2023-04-06T16:50:08Z2000-02-19T20:52:24ZCDS support team

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

cds-question@unistra.frglobular-star-clustersultraviolet-photometryWe present far-ultraviolet images of the globular cluster {omega} Centauri obtained with the Ultraviolet Imaging Telescope (UIT) during the 1990 December Astro-1 mission. A total of 1957 sources are detected at 1620{AA} to a limiting UV magnitude of 16.4 in the central 24' diameter region of the field and a limit of 15.6 over the remainder of the 40' diameter field. Over 1400 of these sources are matched with stars on a Stroemgren u band CCD frame obtained with the CTIO 0.9m telescope to produce a (far-UV, u) color-magnitude diagram. Completeness of the sample and error estimates are determined by photometry of artificial stars added to the images. The horizontal branch (HB) of the CMD is heavily populated hotter than 9000K. A large number of "extreme HB" stars are found hotter than a conspicuous break in the HB at Te~16000K. There is also a significant population of stars above the HB, the brightest of which is 4mag brighter than the HB. Most of the hotter of these appear to be "AGB-manque" or "Post-Early Asymptotic Giant Branch" stars. We compare the observations to recent theoretical evolutionary tracks for the zero-age HB and subsequent phases. The tracks match the data well, with the exception of the hotter HB stars, many of which fall below the zero-age horizontal branch. It is unclear as yet whether these are a special population or an artifact of errors in the models or photometry. We identify 33 stars with Te>~50000K, which are hotter than zero-age HB stars with envelope masses of 0.003M_{sun}_.1994AJ....108.1350Whttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/108/1350CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/108/1350https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/108/1350http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/108/1350https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/108/1350https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/108/1350http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/108/1350GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapUITUVdefaultJ/AJ/108/1350/table3Bright UV sourcesVmag? Dickens et al. (1988) V magnitude (4)magfloatnullablerecnoRecord number assigned by the VizieR team. Should Not be used for identification.intWORSequential number (1)intDxOffset in x position (2)pixfloatDyOffset in y position (2)pixfloatmFUVFUV magnitude, calibrated by IUEmagfloatm3500? 3500{AA} magnitudemagfloatnullabledxu? Offset of the Stroemgren u source position from the predicted centroid of the UIT sourcepixfloatnullabledyu? Offset of the Stroemgren u source position from the predicted centroid of the UIT sourcepixfloatnullableQ1Quality flag on UV-Optical match (3)intQ2Quality flag on Optical imageintQ3Quality flag on UV ImageintB-V? Dickens et al. (1988) B-V colour index (4)magfloatnullableNDi? Dickens et al. (1988) number (4)intnullable