J/A+A/708/A115ivo://CDS.VizieR/J/A+A/708/A115CDSHeber U.Kufleitner L.Dorsch M.Latour M.Dawson H.Mattig F.,Geier S.2026-04-01T08:35:27Z2026-04-01T09:33:28ZCDS support team

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

cds-question@unistra.frhorizontal-branch-starseffective-temperaturechemical-abundancesvisible-astronomyHot subluminous stars (subdwarf B&O, sdB, sdO) are evolved low mass stars originating from red giants that lost their envelope almost entirely. The multitude of observed phenomena imply that several pathways may form hot subdwarfs, most involving close binary channels. The Hamburg Quasar Survey (HQS) has led to the discovery of many faint blue stars, including hot subdwarf stars. Many of the HQS-sdB stars have been studied in detail, but analyses of the helium-rich sdOB and sdO stars are lacking. The recent development of model spectra calculated from model atmopheres in local thermodynamic equilibrium (LTE) allowing for non-LTE departures (hybrid LTE/NLTE model spectra, the 2nd generation Bamberg model grids) enables us to improve the spectroscopic analyses of sdB stars as well as of the previously unstudied sdO stars allowing precise atmospheric parameters to be derived, while consistently accounting for parameter correlations and systematic uncertainties. The Gaia mission provided astrometric data of unprecedented quality, which allow fundamental stellar parameters to be derived from atmospheric parameters via parallax measurements. We used spectral energy distributions to identify composite-colour sdB binaries and present the result of detailed spectroscopic analyses of 122 non-composite subdwarfs from the HQS to identify potential evolutionary pathways. Comparison to evolutionary tracks both in the Kiel (Teff-logg) and the physical Hertzsprung-Russell (Teff-logL) diagram finds the location of the sdB stars on the extreme horizontal branch (EHB). Their derived mass distribution and median mass of 0.45 Msun are consistent with the canonical EHB mass. We revisited the sample of known pulsating HQS-sdB stars and find no significant differences between their mass distributions and those of sdB stars that do not pulsate. The helium-rich sdOB and sdO stars are found near the helium main sequence (He-MS). The derived mass distribution of the extremely He-rich subdwarfs is broader (0.48 to 1.05M_{sun}_) and peaks at a median of 0.70M_{sun}_, significantly larger than those of the hydrogen-rich stars. Intermediate He-rich subdwarfs are also He-MS stars, but of lower mass (0.55M_{sun}_) than the extremely He-rich subdwarfs. This strongly supports the merger scenario for the origin of He-rich sdO stars, in which two helium white dwarfs merge following orbital decay driven by gravitational-wave emission, producing a He-rich sdO or sdOB star. Comparing results from similar studies, we speculate that older populations produce more massive helium white dwarfs mergers.2026A&A...708A.115Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/708/A115CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+AS/134/483 : The Hamburg Quasar Survey. III. (Hagen+ 1999)J/A+A/400/939 : Stellar parameters of 115 HQS sdB stars (Edelmann+, 2003)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/708/A115https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/708/A115http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/708/A115https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/708/A115https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/708/A115http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/708/A115GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/708/A115/tabled1 (Atmospheric and stellar parameters for 103 hot subdwarf stars with parallax uncertainties better than 25%)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/708/A115/tabled1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/708/A115/tabled1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/708/A115/tabled1?GETtext/xml+votable180.050000true6.5106231.105680.005555555555555556Cone search capability for table J/A+A/708/A115/tabled2 (Atmospheric parameters for 12 hot subdwarf stars with parallax uncertainties larger than 25%)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/708/A115/tabled2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/708/A115/tabled2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/708/A115/tabled2?GETtext/xml+votable180.050000true5.4471140.023090.0055555555555555566/443 560 719 723 853 874 894 944 2228 2600 2700 2753 2756 3578 3920 3928 3933 4050 5199 5838 5843 6365 6507 6536 6562 7109 7125 7404 7530 7626 7732 7881 8119 10065 10213 10220 10285 10963 11605 11637 11643 11645 11652-11653 11713 11755 11762 11946 12342 12404 12430 12505 12534 12666 12673 12765 13324 13327 13336 13362-13363 13434 13442 13446 13455 13464 13582 15096 15288 15310 15979 16002 16010 16019 16032 16053 16055 16071 16076 16107 16125 16316 16327 16346 16350 17865 18027 18031 18789 18845 18863 18873 19122 19141 19210 19255 19309 19329 19368 19419 19427 20224 20236 20311 20337 20343 23160 23319 23385 23468 30075 30078-30079 32307 32372https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/708/A115?format=asciiOpticaldefaultJ/A+A/708/A115/tabled1Atmospheric and stellar parameters for 103 hot subdwarf stars with parallax uncertainties better than 25%recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSimbadSimbad column added by the CDSmeta.ref.urlcharNameHQS name (Name)meta.id;meta.maincharRAJ2000Right ascension (J2000) (ra)degpos.eq.ra;meta.mainDEJ2000Declination (J2000) (dec)degpos.eq.dec;meta.mainGaiaDR3Gaia DR3 number (gaia)meta.idClassSpectral class (Class)src.spTypecharTeffEffective temperature (Teff)Kphys.temperature.effectiveintE_TeffUpper uncertainty on Teff (e_Teff)Kstat.error;stat.maxinte_TeffLower uncertainty on Teff (e_Teff)Kstat.error;phys.temperature.effectiveintloggSurface gravity (g) in log (logg)log(cm.s**-2)phys.gravityfloatE_loggUpper uncertainty on logg (e_logg_hi)log(cm.s**-2)stat.error;stat.maxfloate_loggLower uncertainty on logg (e_logg_lo)log(cm.s**-2)stat.errorfloatlogn(He/H)Helium abundance as log (N(He)/N(H) (logn(He/H))phys.abund.YfloatE_logn(He/H)Upper uncertainty on the helium abundance (e_logn(He/H)_hi)stat.error;stat.maxfloate_logn(He/H)Lower uncertainty on the helium abundance (e_logn(He/H)_lo)stat.errorfloatteffdiffszImpact of metallicity on Teff in percent (s. Sect. 3.2) (teff_diffs_z)%stat.fit.paramdoubleloggdiffszImpact of metallicity on logg (s. Sect. 3.2) (logg_diffs_z)stat.fit.paramdoublelogn(He/H)diffszImpact of metallicity on He/H (s. Sect. 3.2) (logn(He/H)_diffs_z)stat.fit.paramdoubleCorrCoeffTeff-logg correlation coefficient (s. Sect. 3.1) (corr_coeff)stat.correlationfloatRStellar Radius (R)solRadphys.size.radiusfloatE_RUpper uncertainty on Radius (e_R_hi)solRadstat.error;stat.maxfloate_RLower uncertainty on Radius (e_R_lo)solRadstat.errorfloatLStellar luminosity (L)solLumphys.luminosityfloatE_LUpper uncertainty on luminosity (e_L_hi)solLumstat.error;stat.maxfloate_LLower uncertainty on luminosity (e_L_lo)solLumstat.errorfloatMStellar mass (M)solMassphys.massfloatE_MUpper uncertainty on mass (e_M_hi)solMassstat.error;stat.maxfloate_MLower uncertainty on mass (e_M_lo)solMassstat.errorfloatplxGaia parallax corrected for zero-point offset (parallax)maspos.parallax.trigfloate_plxUncertainty of Gaia parallax (e_parallax)masstat.error;pos.parallaxfloatE(44-55)Reddening (E(44-55)) from the SED fit (E(44-55))magphot.color.excessfloatE_E(44-55)Upper uncertainty on E(44-55) (e_E(44-55)_hi)magstat.error;stat.maxfloate_E(44-55)Lower uncertainty on E(44-55) (e_E(44-55)_lo)magstat.errorfloatlogthetaAngular diameter as log(theta) (logtheta)log(rad)phys.angSizedoubleE_logthetaUpper uncertainty on log(theta) (e_logtheta_hi)log(rad)stat.error;stat.maxfloate_logthetaLower uncertainty on log(theta) (e_logtheta_lo)log(rad)stat.error;pos.posAngfloatCommentComments (comment) (1)meta.notecharJ/A+A/708/A115/tabled2Atmospheric parameters for 12 hot subdwarf stars with parallax uncertainties larger than 25%ClassSpectral class (Class)src.spTypecharTeffEffective temperature (Teff)Kphys.temperature.effectiveintE_TeffUpper uncertainty on Teff (e_Teff_hi)Kstat.error;stat.maxinte_TeffLower uncertainty on Teff (e_Teff_lo)Kstat.error;phys.temperature.effectiveintSimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameHQS name (Name)meta.id;meta.maincharRAJ2000Right ascension (J2000) (ra)degpos.eq.ra;meta.mainDEJ2000Declination (J2000) (dec)degpos.eq.dec;meta.mainGaiaDR3Gaia DR3 number (gaia)meta.idloggSurface gravity (g) in log (logg)log(cm.s**-2)phys.gravityfloatE_loggUpper uncertainty on logg (e_logg_hi)log(cm.s**-2)stat.error;stat.maxfloate_loggLower uncertainty on logg (e_logg_lo)log(cm.s**-2)stat.errorfloatlogn(He/H)Helium abundance as log (N(He)/N(H) (logn(He/H))phys.abund.YfloatE_logn(He/H)Upper uncertainty on the helium abundance (e_logn(He/H)_hi)stat.error;stat.maxfloate_logn(He/H)Lower uncertainty on the helium abundance (e_logn(He/H)_lo)stat.errorfloatteffdiffszImpact of metallicity on Teff in percent (s. Sect. 3.2) (teff_diffs_z)%stat.fit.paramdoubleloggdiffszImpact of metallicity on log g (s. Sect. 3.2) (logg_diffs_z)stat.fit.paramdoublelogn(He/H)diffszImpact of metallicity on He/H (s. Sect. 3.2) (logn(He/H)_diffs_z)stat.fit.paramdoubleCorrCoeffTeff-logg correlation coefficient (s. Sect. 3.1) (corr_coeff)stat.correlationfloatplx? Gaia parallax corrected for zero-point offset (parallax)maspos.parallax.trigfloatnullablee_plx? Uncertainty of Gaia parallax (e_parallax)masstat.error;pos.parallaxfloatnullableE(44-55)Reddening (E(44-55)) from the SED fit (E(44-55))magphot.color.excessfloatE_E(44-55)Upper uncertainty on E(44-55) (e_E(44-55)_hi)magstat.error;stat.maxfloate_E(44-55)Lower uncertainty on E(44-55) (e_E(44-55)_lo)magstat.errorfloatlogthetaAngular diameter as log(theta) (logtheta)log(rad)phys.angSizedoubleE_logthetaUpper uncertainty on log(theta) (e_logtheta_hi)log(rad)stat.error;stat.maxfloate_logthetaLower uncertainty on log(theta) (e_logtheta_lo)log(rad)stat.error;pos.posAngfloatCommentComments (comment) (1)meta.notechar