J/A+A/707/A6ivo://CDS.VizieR/J/A+A/707/A6CDSDawson H.Dorsch M.Geier S.Munday J.Pritzkuleit M.Heber U.,Mattig F.Benitez-Palacios D.Vuckovic M.Pelisoli I.Deshmukh K.,Bhat A.Kufleitner L.Uzundag M.Schaffenroth V.Reindl N.Culpan R.,Raddi R.Antunes Amaral L.Istrate A.G.Justham S.Ostensen R.H.,Telting J.H.Steinmetz T.Rodriguez-Segovia N.Fernandez-Schlosser P.,Duran-Reyes A.Arancibia-Rojas E.Latour M.Jones G.T.O'Brien M.,Sahu S.Elms A.2026-02-25T08:32:58Z2026-02-25T09:31:23ZCDS support team

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

cds-question@unistra.frsubdwarf-starsstellar-spectral-typesstellar-massesvisible-astronomyWe present a quantitative spectroscopic and kinematic analysis of a volume-complete sample of hot subluminous stars within 500 pc of the Sun, assembled using accurate parallax measurements from the Gaia space mission Data Release 3 (DR3). In total, 3226 spectra of 253 hot subdwarf stars were analysed to derive atmospheric parameters (Teff, logg, and helium abundance) and radial velocities. Spectral energy distributions (SEDs) with Gaia parallaxes were used to measure stellar radii, luminosities, and masses. The derived atmospheric parameters reveal a consistent alignment between sdB and sdO stars in the Kiel diagram when compared to theoretical evolutionary models. Notably, we find a substantial population (about 10%) of hot subdwarfs located below the 0.45M_{sun}_ zero-age extreme horizontal branch (EHB) in both the Kiel and Hertzsprung-Russell diagrams (HRDs), which likely originate from intermediate-mass progenitors (1.8-8M_{sun}_). The overall mass distribution peaks at 0.48_-0.10_^0.14^M_{sun}_, while hot subdwarfs below the EHB peak at 0.43_-0.09_^0.11^M_{sun}_, supporting a scenario of non- or semi-degenerate helium ignition for these objects characteristic of intermediate-mass stars. Interpolation of EHB and post-EHB tracks yields theoretical mass distributions consistent with our estimates based on SED and parallax. By assuming a mass range between 0.40 and 0.50M_{sun}_ during the interpolation, we further find that the post-EHB birthrate in our sample is 2-3 times higher than the EHB birthrate, which may suggest overestimated EHB lifetimes in theoretical tracks or contamination from other formation and evolutionary channels. Our kinematic analysis shows that 86+/-2% of the stars belong to the Galactic thin disk, with 13+/-1% and 1+/-1% associated with the thick disk and halo, respectively. The below-EHB population is exclusively found in the thin disk, the only Galactic population young enough to harbour intermediate-mass stars. The below-EHB population seems to be absent in other large samples, which generally include more thick disk and halo members. These findings suggest that non-degenerate formation channels may play a more prominent role in the Galactic disk than previously thought.2026A&A...707A...6Dhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/707/A6CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/350 : Gaia EDR3 (Gaia Collaboration, 2020)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/707/A6https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/707/A6http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/707/A6https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/707/A6https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/707/A6http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/707/A6GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/707/A6/table2 (Atmospheric parameters)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/707/A6/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/707/A6/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/707/A6/table2?GETtext/xml+votable180.050000true49.408414.77320.005555555555555556Cone search capability for table J/A+A/707/A6/table3 (SED and HRD parameters)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/707/A6/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/707/A6/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/707/A6/table3?GETtext/xml+votable180.050000true49.408414.77320.005555555555555556Cone search capability for table J/A+A/707/A6/table4 (Kinematic/membership parameters)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/707/A6/table4?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/707/A6/table4?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/707/A6/table4?GETtext/xml+votable180.050000true49.408414.77320.0055555555555555566/215 550 573 765 1115 1792 2279 2445 2507 2531 2626 2845 3092 3467 4104 4630 4931 4938 5153 5544 5550 5858 5866 6661 7052 7670 7818 8006 8044 8068 8135 8791 8813 8982 9470 9552 9664 9790 9951 10048 10083 10123 10146 10471 10903 11680 11760 11795 12022 12048 12072 12142 12254 12443 12497 12697 12765 12898 12961 13024 13026 13163 13354 13437 13480 13840 14059 14124 14168 14466 14558 14646 14779 14943 14960 15065 15633 16150 16187 16378 16430 16534 17323 17534 18132 18346 18372 18550 18712 18748 18766 18774 18941 19590 19666 19741 20223 20321 20474 20904 21111 21585 21740 21836 22248 22382 22422 22452 22743 22784 23133 23244 23470 23691 23752 23925 24038 24063 24204 24361 24475 24813 25061 25068 25136 25566 25990 26112 26735 27126 27324 27839 27963 28134 28323 28390 28747 28972-28973 28977 29343 29489 29684 29719 29738 30061-30062 30081 30222 30326 30555 30939 31062 31518 31887 31919 32380 32528 32674 32752 33097 33100 33595 33795 33859 33984 34699 34916 34986 35339 35355 35718 35720 35798 36382 36436 36532 36540 36546 36679 36784 36844 37056 37067 37169 37523 37715 38447 38579 38667 38885 38958 39171 39362 39735 39930 40156 40281 40714 40968 41197 41224 41375 41487 41515 41790 41799 41891 41950 42044 42225 42477 42499 42555 42676 42781 42834 42885 42969 43581 43860 44133 44218 44376 44616 44816 44969 45270 45386 45443 45566 45682 45715 45998 46105 46198 46228 46637 46778 46990 47323 47591 47651 47985-47986 48030 48074 48181 48666 48709 48769 48933 49042https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/707/A6?format=asciiOpticaldefaultJ/A+A/707/A6/table2Atmospheric parametersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameName of objectmeta.id;meta.maincharRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainClassSpectral classificationspect.indexcharTeffEffective temperatureKphys.temperature.effectiveintSimbadNameSimbad column added by the CDSmeta.idcharnullableRVRadial velocitykm/sphys.veloc;pos.heliocentricintloggSurface gravitylog(cm.s**-2)phys.gravityfloatlogm(He)/m(H)Helium abundancephys.abund.YfloatFlag[A/B] Quality flag (A = reliable parameters)meta.code.errorcharJ/A+A/707/A6/table3SED and HRD parametersrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameName of objectmeta.id;meta.maincharRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainMSEDSED masssolMassphys.massdoubleE_MSEDSED mass upper errorsolMassstat.error;stat.maxfloate_MSEDSED mass lower errorsolMassstat.errorfloatLSEDSED luminositysolLumphys.luminositydoubleE_LSEDSED luminosity upper errorsolLumstat.error;stat.maxfloate_LSEDSED luminosity lower errorsolLumstat.errorfloatRSEDSED radiussolRadphys.size.radiusfloatE_RSEDSED radius upper errorsolRadstat.error;stat.maxfloate_RSEDSED radius lower errorsolRadstat.errorfloatE(44-55)Extinction (Stilism)magphot.color.excessfloatE_E(44-55)Extinction (Stilism) upper errormagstat.error;stat.maxfloate_E(44-55)Extinction (Stilism) lower errormagstat.errorfloatMHDR? HDR masssolMassphys.massfloatnullableE_MHDR? HDR mass upper errorsolMassstat.error;stat.maxfloatnullablee_MHDR? HDR mass lower errorsolMassstat.errorfloatnullabletauHRD? HRS ageMyrtime.agefloatnullableE_tauHRD? HDR age upper errorMyrstat.error;stat.maxfloatnullablee_tauHRD? HDR age lower errorMyrstat.errorfloatnullableFlag[A/B] Quality flag (A = reliable parameters)meta.code.errorcharJ/A+A/707/A6/table4Kinematic/membership parameterspthinThin probabilitystat.fit.goodnessfloatpthickThick probabilitystat.fit.goodnessfloatphaloHalo probabilitystat.fit.goodnessfloatMembMenbershipmeta.code.membercharFlag[A/B] Quality flag (A = reliable parameters)meta.code.errorcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameName of objectmeta.id;meta.maincharRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainUvelU velocitykm/sphys.veloc;pos.cartesian.xfloatE_UvelU velocity upper errorkm/sstat.error;stat.maxfloate_UvelU velocity lower errorkm/sstat.errorfloatVvelV velocitykm/sphys.veloc;pos.cartesian.yfloatE_VvelV velocity upper errorkm/sstat.error;stat.maxfloate_VvelV velocity lower errorkm/sstat.errorfloatWvelW velocitykm/sphys.veloc;pos.cartesian.zfloatE_WvelW velocity upper errorkm/sstat.error;stat.maxfloate_WvelW velocity lower errorkm/sstat.errorfloat