J/A+A/627/A34ivo://CDS.VizieR/J/A+A/627/A34doi:10.26093/cds/vizier.36270034CDSMoehler S.Landsman W.B.Lanz T.Miller Bertolami M.M.2019-07-26T12:53:54Z2019-07-01T11:11:02ZCDS support team

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

cds-question@unistra.frastronomical-modelsglobular-star-clustersstellar-populationsultraviolet-astronomyspectroscopyWe have performed a census of the UV-bright population in 78 globular clusters using wide-field UV telescopes. This population includes a variety of phases of post-horizontal branch (HB) evolution, including hot post-asymptotic giant branch (AGB) stars, and post-early AGB stars. There are indications that old stellar systems like globular clusters produce fewer post-(early) AGB stars than currently predicted by evolutionary models, but observations are still scarce. We wish to derive effective temperatures, surface gravities, and helium abundances of the luminous hot UV-bright stars in these clusters to determine their evolutionary status and compare the observed numbers to predictions from evolutionary theory. We obtained FORS2 spectroscopy of 11 of these UV-selected objects (covering a range of -2.3<[Fe/H]<-1.0), which we (re-)analysed together with previously observed data. We used model atmospheres of different metallicities, including super-solar ones. Where possible, we verified our atmospheric parameters using UV spectrophotometry and searched for metal lines in the optical spectra. We calculated evolutionary sequences for four metallicity regimes and used them together with information about the HB morphology of the globular clusters to estimate the expected numbers of post-AGB stars. We find that metal-rich model spectra are required to analyse stars hotter than 40000 K. Seven of the eleven new luminous UV-bright stars are post-AGB or post-early AGB stars, two are evolving away from the HB, one is a foreground white dwarf, and another is a white dwarf merger. Taking into account published information on other hot UV-bright stars in globular clusters, we find that the number of observed hot post-AGB stars generally agrees with the predicted values, although the numbers are still low. Spectroscopy is clearly required to identify the evolutionary status of hot UV-bright stars. For hotter stars, metal-rich model spectra are required to reproduce their optical and UV spectra, which may affect the flux contribution of hot post-AGB stars to the UV spectra of evolved populations. Adding published information on other hot UV-bright stars in globular clusters, we find that the number of observed hot post-AGB stars generally agrees with the predicted values, although the numbers are still low.2019A&A...627A..34Mhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/627/A34CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/627/A34https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/627/A34http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/627/A34https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/627/A34https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/627/A34http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/627/A34GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/627/A34/stars (List of stars with atmospheric parameters and evolutionary status)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/627/A34/stars?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/627/A34/stars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/627/A34/stars?GETtext/xml+votable180.050000true201.7710833-47.36572220.0055555555555555566/14489 28973 29870 37294 42955 43225 43227 47168 47825 48434https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/627/A34?format=asciiUVdefaultJ/A+A/627/A34/fors2-fFlux-calibrated FORS2 spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelengthnmem.wldoubleOCen-UIT151? Flux-calibrated spectrum for NGC5139-UIT15110mW.m**-2.nm**-1phot.flux;meta.modelleddoublenullableOCen-UIT644? Flux-calibrated spectrum for NGC5139-UIT64410mW.m**-2.nm**-1phot.flux;meta.modelleddoublenullableOCen-UIT1275? Flux-calibrated spectrum for NGC5139-UIT127510mW.m**-2.nm**-1phot.flux;meta.modelleddoublenullableOCen-UIT1425? Flux-calibrated spectrum for NGC5139-UIT142510mW.m**-2.nm**-1phot.flux;meta.modelleddoublenullableOCen-Dk3873? Flux-calibrated spectrum for NGC5139-Dk387310mW.m**-2.nm**-1phot.flux;meta.modelleddoublenullableOCen-ROA5342? Flux-calibrated spectrum for NGC5139-ROA534210mW.m**-2.nm**-1phot.flux;meta.modelleddoublenullableNGC6121-U2? Flux-calibrated spectrum for NGC6121-UVBS210mW.m**-2.nm**-1phot.flux;meta.modelleddoublenullableNGC6656-U1n? Flux-calibrated spectrum for NGC6656-UVBS2 (narrow extraction)10mW.m**-2.nm**-1phot.flux;meta.modelleddoublenullableNGC6656-U1c? Flux-calibrated spectrum for NGC6656-UVBS2 (companion corrected)10mW.m**-2.nm**-1phot.flux;meta.modelleddoublenullableNGC6712-C49? Flux-calibrated spectrum for NGC6712-C4910mW.m**-2.nm**-1phot.flux;meta.modelleddoublenullableNGC6779-ZNG2? Flux-calibrated spectrum for NGC6779-ZNG210mW.m**-2.nm**-1phot.flux;meta.modelleddoublenullableNGC7099-U2? Flux-calibrated spectrum for NGC7099-UVBS210mW.m**-2.nm**-1phot.flux;meta.modelleddoublenullableJ/A+A/627/A34/lteBest-fitting LTE model spectralambdaWavelengthnmem.wlfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintN2808-C2946? Metal-poor best fit LTE model spectrum for NGC2808-C2946phot.flux;meta.modelleddoublenullableN2808-C2947? Metal-poor best fit LTE model spectrum for NGC2808-C2947phot.flux;meta.modelleddoublenullableN2808-C4594? Metal-poor best fit LTE model spectrum for NGC2808-C4594phot.flux;meta.modelleddoublenullableOCen-ROA542? Metal-poor best fit LTE model spectrum for NGC5139-ROA542phot.flux;meta.modelleddoublenullableOCen-ROA3596? Metal-rich best fit LTE model spectrum for NGC5139-ROA3596phot.flux;meta.modelleddoublenullableOCen-UIT1275? Metal-rich best fit LTE model spectrum for NGC5139-UIT1275phot.flux;meta.modelleddoublenullableOCen-UIT1425? Metal-rich best fit LTE model spectrum for NGC5139-UIT1425phot.flux;meta.modelleddoublenullableN6723-IV9? Metal-poor best fit LTE model spectrum for NGC6723-IV9phot.flux;meta.modelleddoublenullableN6752-B2004? Metal-poor best fit LTE model spectrum for NGC6752-B2004phot.flux;meta.modelleddoublenullableJ/A+A/627/A34/wdmodelBest-fitting metal-free NLTE model spectrum for NGC7099-UVBS2recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelengthnmem.wlfloatN7099-UVBS2? Metal-free best fit NLTE model spectrum for NGC7099-UVBS2phot.flux;meta.modelleddoublenullableJ/A+A/627/A34/starsList of stars with atmospheric parameters and evolutionary statusClusterGlobular cluster namemeta.id.parentcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStarStar namemeta.id;meta.maincharRAJ2000Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainTeffEffective temperatureKphys.temperature.effectiveintlogglogarithmic surface gravitylog(cm.s**-2)phys.gravityfloatlogHe/Hlogarithmic helium abundance by particle number relative to hydrogenphys.abund.YfloatStatusEvolutionary statussrc.classcharEFOSC2-NName of the column with fluxes in efosc2-n.dat tablemeta.codecharsp1Show the normalized EFOSC2 spectrummeta.ref.urlcharFORS2Name of the column with fluxes in fors2-n.dat and fors2-f.dat tablesmeta.codecharsp2Show the normalized and flux-calibrated FORS2 spectrameta.ref.urlcharLTEName of the column with fluxes in lte.dat tablemeta.codecharsp3Show the best-fitting LTE model spectrummeta.ref.urlcharNLTEName of the column with fluxes in nlte.dat tablemeta.codecharsp4Show the best-fitting NLTE model spectrummeta.ref.urlcharWDmodelName of the column with fluxes in wdmodel.dat tablemeta.codecharsp5Show the best-fitting metal-free NLTE model spectrummeta.ref.urlcharJ/A+A/627/A34/efosc2-nNormalized EFOSC2 spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelengthnmem.wlfloatOCen-ROA542? Normalized spectrum for NGC5139-ROA542phot.flux;meta.modelleddoublenullableOCen-ROA3596? Normalized spectrum for NGC5139-ROA3596phot.flux;meta.modelleddoublenullableJ/A+A/627/A34/fors2-nNormalized FORS2 spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelengthnmem.wlfloatOCen-UIT151? Normalized spectrum for NGC5139-UIT151phot.flux;meta.modelleddoublenullableOCen-UIT644? Normalized spectrum for NGC5139-UIT644phot.flux;meta.modelleddoublenullableOCen-UIT1275? Normalized spectrum for NGC5139-UIT1275phot.flux;meta.modelleddoublenullableOCen-UIT1425? Normalized spectrum for NGC5139-UIT1425phot.flux;meta.modelleddoublenullableOCen-Dk3873? Normalized spectrum for NGC5139-Dk3873phot.flux;meta.modelleddoublenullableOCen-ROA5342? Normalized spectrum for NGC5139-ROA5342phot.flux;meta.modelleddoublenullableNGC6121-U2? Normalized spectrum for NGC6121-UVBS2phot.flux;meta.modelleddoublenullableNGC6656-U1n? Normalized spectrum for NGC6656-UVBS2 (narrow extraction)phot.flux;meta.modelleddoublenullableNGC6656-U1c? Normalized spectrum for NGC6656-UVBS2 (companion corrected)phot.flux;meta.modelleddoublenullableNGC6712-C49? Normalized spectrum for NGC6712-C49phot.flux;meta.modelleddoublenullableNGC6779-ZNG2? Normalized spectrum for NGC6779-ZNG2phot.flux;meta.modelleddoublenullableNGC7099-U2? Normalized spectrum for NGC7099-UVBS2phot.flux;meta.modelleddoublenullableJ/A+A/627/A34/nlteBest-fitting NLTE model spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelengthnmem.wlfloatOCen-UIT151? Metal-rich best fit NLTE model spectrum for NGC5139-UIT151phot.flux;meta.modelleddoublenullableOCen-UIT644? Metal-poor best fit NLTE model spectrum for NGC5139-UIT644phot.flux;meta.modelleddoublenullableOCen-Dk3873? Metal-rich best fit NLTE model spectrum for NGC5139-Dk3873phot.flux;meta.modelleddoublenullableOCen-ROA5342? Metal-rich best fit NLTE model spectrum for NGC5139-ROA5342phot.flux;meta.modelleddoublenullableN6121-Y453? Metal-rich best fit NLTE model spectrum for NGC6121-Y453phot.flux;meta.modelleddoublenullableN6121-UVBS2? Metal-rich best fit NLTE model spectrum for NGC6121-UVBS2phot.flux;meta.modelleddoublenullableN6656-UVBS2n? Metal-rich best fit NLTE model spectrum for NGC6656-UVBS2phot.flux;meta.modelleddoublenullableN6712-C49? Metal-rich best fit NLTE model spectrum for NGC6712-C49phot.flux;meta.modelleddoublenullableN6723-III60? Metal-rich best fit NLTE model spectrum for NGC6723-III60phot.flux;meta.modelleddoublenullableN6779-ZNG2? Metal-poor best fit NLTE model spectrum for NGC6779-ZNG2phot.flux;meta.modelleddoublenullable