J/A+A/705/A248ivo://CDS.VizieR/J/A+A/705/A248CDSLatour M.Green E.M.Dorsch M.Van Grootel V.Chayer P.Charpinet S.,Heber U.Randall S.K.Ma X.-Y.2026-03-02T06:25:50Z2026-01-28T08:55:29ZCDS support team

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

cds-question@unistra.frsubdwarf-starsstellar-masseshertzsprung-russell-diagramfaint-blue-starseffective-temperaturespectroscopyhorizontal-branch-starsHot subdwarf B (sdB) and O (sdO) type stars are evolved helium-burning objects that lost their hydrogen envelope before the helium flash when their progenitors were close to the tip of the red giant branch. They populate the extreme horizontal branch (EHB) in the Hertzsprung-Russel diagram (HRD). The mass distribution of canonical hot subdwarfs is expected to peak at the core mass required for helium ignition under degenerate conditions, in the 0.45 to 0.5M_{sun}_ range. However, non-degenerate helium ignition from intermediate-mass progenitor and non-canonical pathways, such as the merger of helium white dwarfs and delayed helium flashes, are also expected to contribute to the hot subdwarf population. Using the high-quality, homogeneous spectra of 336 hot subluminous star candidates from the Arizona-Montreal Spectroscopic Survey, we aim to improve our understanding of the atmospheric and stellar properties of hot subdwarf stars. Our focus is on the mass distribution of the different types of hot subdwarfs and their connections to the various formation scenarios. We used large grids of model atmospheres to fit the observed spectra and derived their atmospheric parameters: effective temperature (Teff), surface gravity, and helium abundance. The model grids were further utilized to fit the spectral energy distribution of each star and the Gaia parallax was used to compute the stellar parameters radius, luminosity, and mass. Our spectroscopic sample mostly consists of H-rich sdBs and sdOs, but also contains 41 He-rich sdOs. Additionally, the sample includes 11 intermediate-helium stars and 19 horizontal branch objects with Teff>~14kK. We detected the presence of helium stratification in six sdB stars with T eff around 30kK, making them good candidates for also showing 3 He enrichment in their atmospheres. Our sdB distribution along the EHB shows a gap near 33kK, visible in both the Kiel (logg-Teff ) diagram and HRD, corroborating previous observations and predictions. The mass distributions of H-rich sdBs and sdOs are similar and centered around 0.47M_{sun}_, consistent with the canonical formation scenario of helium ignition under degenerate conditions. Among the H-rich hot subdwarfs, we found no difference between the mass distributions of close binaries and apparently single stars. The He-sdOs have a significantly wider mass distribution than their H-rich counterparts, with an average mass of about 0.78M_{sun}_. In the HRD, the He-sdOs lie on the theoretical helium main sequence for masses between 0.6 and 1M_{sun}_. This strongly favors a merger origin for these He-rich objects. We identified a small number of candidate low-mass (<0.45M_{sun}_) sdBs located below the EHB that might have originated from more massive progenitors. These low-mass sdBs preferentially show low helium abundances. Finally, we identified more than 80 pulsating stars in our sample and find these to fall into well-defined p- and g-mode instability regions.2026A&A...705A.248Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/705/A248CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toJ/A+A/684/A118 : Pulsating hot subdwarf B stars (Uzundag+, 2024)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/705/A248https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/705/A248http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/705/A248https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/705/A248https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/705/A248http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/705/A248GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/705/A248/tabled1 (Properties of the stars in the Bok sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/705/A248/tabled1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/705/A248/tabled1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/705/A248/tabled1?GETtext/xml+votable180.050000true140.329981.724340.0055555555555555566/43 136 194 215 226 550 573 596 664 715 719 723 764-765 944 1004 1957 2188 2243 2437 2616 2753 2965 2981 3467 3928 3933 4078 4104 4123 4285 4293 4297 4319 4345-4346 4497 4560 4604 4610 4630 4689 4709 4790 4899 4902 4931 4938 5021 5153 5544 5550 5655 5710 5761 5818 5858 5866 5884 5917-5918 5947 6108 6507 6651 7125 7259 7333 7583 7670 7719 7779 7830 8016 8044 8068 8135 8245 8284 8447 8518 8570 8671 8696 8770 8791 8806 8813 8830 8923 8958 8982 9215 9239 9436 9470 9516 9552 9640 9664 9683 9690 9720 9775 9790 9819 9951 10017 10019 10048 10088 10123 10144 10146 10159 10214 10333 10345 10378-10379 10471 10624 10629 10636 10903 11029 11038 11047 11145 11157 11159 11171 11264 11303 11335 11680 11795 11813 11942 12022 12072 12142 12200 12443 12765 12922 12961 13024 13286 13319 13339 13362 13405 13442 13480 13555 13561 13646 13704 13806 13961 13999 14135 14217 14396 14485 14770 14772 14915 14921 14960-14961 15023 15065 15128 15132 15137 15285 16187 16346 17318 17322-17323 17534 17726 17789 18132 18194 18346 18372 18391 18418 18454 18548 18550 18712 18716 18748 18766 18774 18890 18906 18941 18962 18966 19033 19130 19159 19210 19361 19368-19369 19372 19419 19475 19528 19590 19649 19666 19705 19710 19726 19741 19802 19874 19898 19942 19962 20055 20118 20165 20218 20223 20236 20279 20321 20383 21804 21836 22169 22304 22784 23157 23244 23285 23319 23385 23468 23470 23510 23516 23925 24204 25068 25545 25584 25700 25719 25740 25845 25882 25915 25921 25927 25957 25990 26087 26112 26138 26184 26299 26348 26351 26453 26517 26609 26748 26780 26808 26837 26854 26883 27000 27045 27082 27099 27126 27187 27286 27324 27379 27839 27871 27905 27956 27963 27978 28134 28266 28323 28335 28378 28390 28415 28586 30061 30939 31491 31518 31549 31592 31595 31622 31683 31715 32072 32296 32372 32380 32476 32674 32752 36679 36844 36851 40948 45011 48933https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/705/A248?format=asciidefaultJ/A+A/705/A248/tabled1Properties of the stars in the Bok samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameStar namemeta.id;meta.maincharRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainTICTESS Input Catalog numbermeta.idspShow the spectrummeta.ref.urlcharspectraFilename of the spectrum ascii file in subdirectory spmeta.id;meta.filecharSimbadSimbad column added by the CDSmeta.ref.urlcharRUWERUWE value from Gaia EDR3stat.errorfloatplxParallax value from Gaia EDR3maspos.parallax.trigfloate_plxParallax error from Gaia EDR3masstat.error;pos.parallaxfloatSpTypeSpectral type as defined in the papersrc.spTypecharTeffEffective temperatureKphys.temperature.effectiveintE_TeffUpper uncertainty on TeffKstat.error;stat.maxinte_TeffLower uncertainty on TeffKstat.error;phys.temperature.effectiveintloggSurface gravity (g) in loglog(cm.s**-2)phys.gravityfloatE_loggUpper uncertainty on logglog(cm.s**-2)stat.error;stat.maxfloate_loggLower uncertainty on logglog(cm.s**-2)stat.errorfloatlogHeHelium abundance as log (N(He)/N(H)phys.abund.YfloatE_logHeUpper uncertainty on the helium abundancestat.error;stat.maxfloate_logHeLower uncertainty on the helium abundancestat.errorfloatgridModel grid used for the spectral fitmeta.id;stat.fitcharlogthetaSolid angle {theta} (2*R/D) in logsolRadphys.angSizedoublee_logthetaLower uncertainty on log(theta)solRadstat.error;pos.posAngfloatE_logthetaUpper uncertainty on log(theta)solRadstat.error;stat.maxfloatE(44-55)Reddening (E(44-55)) from the SED fitmagphot.color.excessfloate_E(44-55)Lower uncertainty on E(44-55)magstat.errorfloatE_E(44-55)Upper uncertainty on E(44-55)magstat.error;stat.maxfloatRadiusStellar RadiussolRadphys.angSize;srcfloate_RadiusLower uncertainty on RadiussolRadstat.error;phys.size.radiusfloatE_RadiusUpper uncertainty on RadiussolRadstat.error;stat.maxfloatLumStellar luminositysolLumphys.luminosityfloate_LumLower uncertainty on LumsolLumstat.errorfloatE_LumUpper uncertainty on LumsolLumstat.error;stat.maxfloatMassStellar masssolMassphys.massfloate_MassLower uncertainty on MasssolMassstat.error;phys.massfloatE_MassUpper uncertainty on MasssolMassstat.error;stat.maxfloatSEDbinary[01] SED binary code (1)meta.codecharSEDgood[01] SED good code (2)meta.codecharpulsationPulsation properties (3)meta.codecharbinarityBinary properties (Sect.5.4) (4)meta.codecharbEHB[0/1] 1 if the star is below the EHB (Sect.5.3)meta.codeintMhems? Mass obtained from the ZAHeMS in the HRDsolMassphys.massfloatnullablee_Mhems? Lower uncertainty on MhemssolMassstat.errorfloatnullableE_Mhems? Upper uncertainty on MhemssolMassstat.error;stat.maxfloatnullable