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dc.contributor.authorWerner, Klauspt_BR
dc.contributor.authorRauch, Thomaspt_BR
dc.contributor.authorKepler, Souza Oliveirapt_BR
dc.date.accessioned2014-11-15T02:15:41Zpt_BR
dc.date.issued2014pt_BR
dc.identifier.issn0004-6361pt_BR
dc.identifier.urihttp://hdl.handle.net/10183/106960pt_BR
dc.description.abstractWe have detected 21 new, very hot hydrogen-deficient (pre-) white dwarfs (spectral types O(He), hot DO, PG1159) in the Data Release 10 of the Sloan Digital Sky Survey. We present the results of non-local thermodynamic equilibrium (non-LTE) model-atmosphere analyses. The seven PG1159 stars have effective temperatures and surface gravities in the ranges Teff = 100 000–140 000K and log g = 6–7.5. The hottest one is a new member of the rare hybrid-PG1159 subtype, indicating the presence of residual hydrogen. The ten new hot DOs span Teff = 65 000–120 000 K and log g = 7.5–8. Carbon abundances were derived and it is found that the PG1159 star values (C/He = 0.33–0.03 by number) and the DO values (<0.0004–0.01) cover distinct but adjacent ranges. With the discovery of four new O(He) stars (Teff = 80 000–100 000 K, log g = 5–5.5, C/He = 0.002–0.01), we double the number of known members of this rare spectral class. One of them is particularly interesting because it is unusually rich in C, N, O, and Si. Unexpected problems arose with the DOs because many He ii lines of every other star are so deep that they cannot be matched by any model. This is most conspicuous in the case of one object which exhibits the occurrence of ultrahigh-ionization metal features, a hitherto unexplained phenomenon that is known from a disquieting large fraction of hot DOs.en
dc.format.mimetypeapplication/pdf
dc.language.isoengpt_BR
dc.relation.ispartofAstronomy and astrophysics. Les Ulis. Vol. 564 (Apr. 2014), A53, 8 p.pt_BR
dc.rightsOpen Accessen
dc.subjectStars: abundancesen
dc.subjectAnãs brancaspt_BR
dc.subjectEvolucao estelarpt_BR
dc.subjectStars: atmospheresen
dc.subjectStars: evolutionen
dc.subjectStars: AGB and post-AGBen
dc.subjectWhite dwarfsen
dc.subjectStars: fundamental parametersen
dc.titleNew hydrogen-deficient (pre-) white dwarfs in the Sloan Digital Sky Survey Data Release 10pt_BR
dc.typeArtigo de periódicopt_BR
dc.identifier.nrb000942852pt_BR
dc.type.originEstrangeiropt_BR


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