J/MNRAS/521/1674ivo://CDS.VizieR/J/MNRAS/521/1674doi:10.26093/cds/vizier.75211674CDSCrawford C.L.Tisserand P.Clayton G.C.Soon J.Bessel M.Wood P.,Garcia-Hernandez D.A.Ruiter A.J.Seitenzahl I.R.2024-08-22T20:17:04Z2023-04-18T17:10:04ZCDS support team

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

cds-question@unistra.frstar-atlasesstellar-spectral-typesvariable-starscarbon-starsStellar spectral classification has been highly useful in the study of stars. While there is a currently accepted spectral classification system for carbon stars, the subset of hydrogen-deficient carbon (HdC) stars has not been well described by such a system, due predominantly to their rarity and their variability. Here we present the first system for the classification of HdCs based on their spectra, which is made wholly on their observable appearance. We use a combination of dimensionality reduction and clustering algorithms with human classification to create such a system with eight total classes corresponding to temperature, and an additional second axis corresponding to the carbon molecular band strength. We classify over half of the known sample of HdC stars using this, and roughly calibrate the temperatures of each class using their colours. Additionally, we express trends in the occurrence of certain spectral peculiarities such as the presence of hydrogen and lithium lines. We also present three previously unpublished spectra, report the discovery of two new Galactic dustless HdC stars, and additionally discuss one especially unique star that appears to border between the hottest HdCs and the coolest extreme helium stars.2023MNRAS.521.1674Chttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/521/1674CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/521/1674https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/521/1674http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/521/1674https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/521/1674https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/521/1674http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/521/1674GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/521/1674/table2 (HdC spectral classes at or near maximum light)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/521/1674/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/521/1674/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/521/1674/table2?GETtext/xml+votable180.050000true263.9011666750.411072220.005555555555555556Associated datahttps://cdsarc.cds.unistra.fr/assocdata/?obs_collection=J/MNRAS/521/16745/7227 6/1954 3726 3827 8701 9720 12239 12842 14307 14546 14626 15065 24147 24935 28678 28690 28712 28717-28719 28726 28735 28769 28774-28775 28783 28785-28786 28805 28829 28834 28836 28838 28842 28844 28849 28851 28857 28866 28870 28872 28881 28887 28893 28902 28904-28905 28907 28970 29000 29052 29067 29080 29083 29089 29106 29111 29136 29166 29168 29170 29173 29178 29184 29194 29210 29214 29217 29244 29252 29255 29257 29261 29303 29386 29442 29449 29464 29604 29619 29635 29841 30122 30171 30208 30222 30239 30282 30335 30339 30383 30637 30650 30712 30740 32019 32023 32076 33047 33050 33053 33055 33077 33088-33090 33095-33098 33102-33103 33120-33121 33292 33294-33295 33327 33795 37408 37418 37929 38333 40272 41178 41279 41438 41462 41471 41535 41630 41718 41788 41862 42139 42186 42192 42194 42203 42218 42236 42300 42335 42337 42341 42359 42367 42399 42479 42481 42491 42506 42556 42692 42759 42820 43161 43378 44328 45693 46004 47661 47674 47814 47869 47895 47919 47995 48038 48507 488012.367228618189496e-19 3.852589004194616e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/521/1674?format=asciidefaultJ/MNRAS/521/1674/table2HdC spectral classes at or near maximum lightSimbadSimbad column added by the CDSmeta.ref.urlcharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintCode[123] Code (1)meta.codecharspindicates spectrameta.ref.urlcharNameStar namemeta.id;meta.maincharprimaryRAJ2000Right ascension (J2000)pos.eq.ra;meta.mainDEJ2000Declination (J2000)pos.eq.dec;meta.mainInst[WDT] Instrument Codemeta.code;instrcharl_AVLimit flag on AVmeta.code.errorcharAVV-band extinctionmagphys.absorptionfloatTempGroupTemperature group (warm, mild, cool)meta.notecharClassHdC Spectral Typesrc.spTypecharPhotStatusPhotometric Status at Observationmeta.codecharObs.dateObservation Datetime.epoch;obsnullablediscRefDiscovery Paper Reference, in refs.dat filemeta.bibcharVmag? V-band Magnitudemagphot.mag;em.opt.VfloatnullableImag? I-band Magntiudemagphot.mag;em.opt.IfloatnullableSimbadIdSIMBAD Identifier (2)meta.idcharJ/MNRAS/521/1674/refsReferencesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRefReference codemeta.notecharBibCodeBibCodemeta.bib.bibcodecharAutAuthor's namemeta.bib.authorcharComCommentsmeta.notecharJ/MNRAS/521/1674/listList of individual fits spectrarecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintNameStar namemeta.id;meta.maincharNxNumber of pixels along X-axismeta.numberintObs.dateObservation datestime.epoch;obsnullableblambdaLower value of wavelength interval0.1nmem.wldoubleBlambdaLower value of wavelength interval0.1nmem.wldoubledlambdaWavelentgh resolution0.1nmpos.angResolutiondoublesizeSize of FITS fileKibytephys.size;meta.fitsintspShow the spectrummeta.ref.urlcharFileNameName of FITS file, in subdirectory spmeta.id;meta.fitscharTitleTitle of the FITS filemeta.title;meta.fitscharAssocDataAssociated Data web pagemeta.ref.urlchar