J/A+A/711/A70ivo://CDS.VizieR/J/A+A/711/A70CDSGarcia-Zamora E.M.Torres S.Rebassa-Mansergas A.Ferrer-Burjachs A.2026-07-06T07:25:39Z2026-07-06T08:24:25ZCDS support team

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

cds-question@unistra.frwhite-dwarf-starsmorgan-keenan-classificationvisible-astronomyThe latest Gaia data release provides astrometric measurements for 1.8 billion sources and low-resolution spectra for 220 million, including approximately 100 000 white dwarfs. Although useful for pre-classification, Gaia spectra lack the resolution required for accurate spectral typing and reliable parameter determination, motivating dedicated spectroscopic follow-up observations. We assess the reliability of machine-learning spectral classifications derived from Gaia spectra through comparison with medium-resolution spectroscopy.We determine the nature of objects classified as "massive helium-rich (DB)" white dwarfs by automated methods, and characterise the properties of warm and hot DQ (carbon-dominated) white dwarfs, as well as magnetic and metal-polluted objects. We observed 255 white dwarfs along the Gaia B and Q branches with the Gran Telescopio Canarias equipped with the OSIRIS instrument (R~1000). Spectral types were assigned through visual inspection and compared with machine-learning classifications applied to Gaia spectra. For objects labelled as "massive DBs", we independently determined their atmospheric spectral composition. Magnetic white dwarfs were identified via Zeeman splitting, and first-order magnetic field strengths were estimated when possible. Machine-learning classifications are highly accurate (>90% for spectral types included in their training sets), despite the low resolution of Gaia spectra. We determine the true nature of objects classified as "massive DBs" to be largely composed of magnetic white dwarfs and warm DQs, with only 5 of 112 observed objects (4.46%) confirmed as genuine DBs. Warm DQs are found along the Gaia Q branch and exhibit unusually high tangential velocities. We provide spectral classifications for 255 white dwarfs and demonstrate that Random Forest algorithms reliably classify low-resolution Gaia spectra for the main spectral types. We also determine the nature of objects classified as "massive DBs" and identify a large population of magnetic white dwarfs and carbon-rich objects. Several rare subtypes are identified, including 2 DAB, 1 DBAZ, 1 DZAB, 2 DZBA, 14 DAH, 1 DAQ, 1 DQZA, 4 hot and 29 warm DQ stars, along with 63 magnetic white dwarfs. The location and kinematics of warm DQs are consistent with previous studies, supporting their proposed origin as merger remnants.2026A&A...711A..70Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/711/A70CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/711/A70https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/711/A70http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/711/A70https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/711/A70https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/711/A70http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/711/A70GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/711/A70/catalog (Catalog of predicted spectral type, observational types and subtypes for all 255 objects observed by GTC (Table 3))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/711/A70/catalog?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/711/A70/catalog?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/711/A70/catalog?GETtext/xml+votable180.050000true0.331395609085458.20110669486080.0055555555555555566/110 267 315 363 436 439 833 853 1109 1122 1125 1331 1351 1524 1576 1659 1774 1785 1795 1863 1882 1889 1896 1902 1992 2008 2369 2393 2395 2564 2588 2736 2850 2969 2978 3001 3003 3012 3027 3091 3193 3195 3318 3347 3372 3382 3390 3443 3445 3478 3484 3557 3615 3811 3892 3977 4033 4125 4585 5023 5133 6152 6329 6443 6783 6846 6869 6938 6956 7005 7023 7054 7147 7405 7712 7723 7726 7846 7865 7905 7965 8072 8101 8117 8151 8766 8985 9045 9580 9867 10077 11131 11395 11625 11733 11741 11964 11987 12126 12497 12859 12911 12957 13049 13732 14140 14204 14296 14466-14467 14545 14594 14661 14688 14733 14808 14916 15043-15044 15301 15359 15642 15680 15689 15879 15881 15945 16066 16071 16895 18706 18795 18916 19236 19318 19394 19463 20037 20281 20331 20377 20948 21276 21295-21296 21327 21395 21456 21580 21601 21633 21653 21714 21890 21982 22033 22130 22187 22217 22259 22343-22344 22373 22431 22464 22571 22631 22667 22680 22768 22810 22841 22924 22941 22958 23036 23110 23164 23201 23230 23242 23319 23437 23451 23496 23608 23620 23643 23703 23774 23781 23806 23814 23876 23906 23933 23959 23962 24073 24221 24238 24304-24305 24326 24354 24357 24397-24398 24500 24513 25686 25722 25724 25780 25797 25817 26429 26431 26727 26836 26915 27656 27738 28536 29400 29968 30005 30026 30180 30262 30813 31176 31283 31818 31827 31952 31965 31990 32116 32124 32180 32325 32554 36676 40438 40698 40753 40760 40786 40800 40858 40867 40877 40916https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/711/A70?format=asciiOpticaldefaultJ/A+A/711/A70/catalogCatalog of predicted spectral type, observational types and subtypes for all 255 objects observed by GTC (Table 3)recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameName of object (JHHMM+DDMM)meta.id;meta.maincharGaiaDR3Object Gaia designationmeta.idRA_ICRSRight ascension (ICRS) at Ep=2016.0degpos.eq.ra;meta.mainDE_ICRSDeclination (ICRS) at Ep=2016.0degpos.eq.dec;meta.mainPredTypePredicted spectral type of objectsrc.spTypecharObsTypeObservational spectral type of objectsrc.spTypecharObsSubtypeObservational spectral subtype of objectsrc.spTypecharl_B[~<>] Limit flag on Bmeta.code.errorcharB? Magnetic field estimate of objectMGphys.magFieldfloatnullablee_B? Magnetic field estimate of object errorMGstat.errorfloatnullableSimbadSimbad column added by the CDSmeta.ref.urlchar