J/AJ/146/85ivo://CDS.VizieR/J/AJ/146/85doi:10.26093/cds/vizier.51460085CDSHillenbrand L.A.Hoffer A.S.Herczeg G.J.2026-01-13T18:54:37Z2014-07-10T13:45:46ZCDS support team

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

cds-question@unistra.fropen-star-clusterspre-main-sequence-starsstellar-spectral-typesWe report new spectral types or spectral classification constraints for over 600 stars in the Orion Nebula Cluster (ONC) based on medium resolution (R{approx}1500-2000) red optical spectra acquired using the Palomar 200" and Kitt Peak 3.5m telescopes. Spectral types were initially estimated for F, G, and early K stars from atomic line indices while for late K and M stars, which constitute the majority of our sample, indices involving TiO and VO bands were used. To ensure proper classification, particularly for reddened, veiled, or nebula-contaminated stars, all spectra were then visually examined for type verification or refinement. We provide an updated spectral type table that supersedes previous work, increasing the percentage of optically visible ONC stars with spectral type information from 68% to 90%. However, for many objects, repeated observations have failed to yield spectral types primarily due to the challenges of adequate sky subtraction against a bright and spatially variable nebular background. The scatter between our new and our previously determined spectral types is approximately two spectral sub-classes. We also compare our grating spectroscopy results with classification based on narrow-band TiO filter photometry, finding similar scatter. While the challenges of working in the ONC may explain much of the spread, we highlight several stars showing significant and unexplained bona fide spectral variations in observations taken several years apart; these and similar cases could be due to a combination of accretion and extinction changes. Finally, nearly 20% of ONC stars exhibit obvious CaII triplet emission indicative of strong accretion.2013AJ....146...85Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/AJ/146/85CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/171 : Parenago Catalog of Stars in Orion Nebula (Parenago 1954)J/ApJ/722/1092 : Optical photometry of the ONC. II. (Da Rio+, 2010)J/ApJ/677/401 : Xray properties of protostars in ONC (Prisinzano+, 2008)J/ApJ/671/605 : NGC 2264 and ONC PMS stars in the infrared (Cieza+, 2007)J/AJ/134/2272 : Visual binaries in the Orion Nebula Cluster (Reipurth+, 2007)J/ApJ/646/297 : Spitzer observations of pms stars (Rebull+, 2006)J/A+A/458/461 : Binary stars in the Orion Nebula Cluster (Koehler+, 2006)J/AJ/129/363 : Spectroscopy in Orion Nebula Cluster (Sicilia-Aguilar+, 2005)J/ApJ/574/258 : X-ray-emitting young stars in Orion (Feigelson+, 2002)J/AJ/113/1733 : Orion Nebula Cluster population (Hillenbrand 1997)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/AJ/146/85https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/AJ/146/85http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/AJ/146/85https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/AJ/146/85https://vizier.iucaa.in/viz-bin/votable?-source=J/AJ/146/85http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/AJ/146/85GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/AJ/146/85/table2 (ONC spectral types)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/AJ/146/85/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/AJ/146/85/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/AJ/146/85/table2?GETtext/xml+votable180.050000true83.548-5.50547220.0055555555555555566/21438-21439 22804-22805https://cdsarc.cds.unistra.fr/viz-bin/moc/J/AJ/146/85?format=asciidefaultJ/AJ/146/85/table2ONC spectral typesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintStar[1/9326] Star identifier (1)meta.id;meta.mainintm_Star[ab] Component (a or b)meta.code.multipcharf_Star[e] Plate defects or nebular knots (2)meta.codecharRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.mainSimbadSimbad column added by the CDSmeta.ref.urlcharSpT2Newly reported spectral type (4)src.spTypecharf_SpT2[f] Nebular contamination (5)meta.codecharSpT1Previously reported spectral type (3)src.spTypechar