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dc.contributor.authorTremblay, Pier-Emmanuelpt_BR
dc.contributor.authorKepler, Souza Oliveirapt_BR
dc.contributor.authorTorres, Sergiopt_BR
dc.date.accessioned2021-02-16T04:06:14Zpt_BR
dc.date.issued2020pt_BR
dc.identifier.issn0035-8711pt_BR
dc.identifier.urihttp://hdl.handle.net/10183/217994pt_BR
dc.description.abstractWe present a spectroscopic survey of 230 white dwarf candidates within 40 pc of the Sun from the William Herschel Telescope and Gran Telescopio Canarias. All candidates were selected from Gaia Data Release 2 (DR2) and in almost all cases, had no prior spectroscopic classifications. We find a total of 191 confirmed white dwarfs and 39 main-sequence star contaminants. The majority of stellar remnants in the sample are relatively cool (⟨Teff⟩ = 6200 K), showing either hydrogen Balmer lines or a featureless spectrum, corresponding to 89 DA and 76 DC white dwarfs, respectively. We also recover two DBA white dwarfs and 9–10 magnetic remnants. We find two carbon-bearing DQ stars and 14 new metal-rich white dwarfs. This includes the possible detection of the first ultra-cool white dwarf with metal lines. We describe three DZ stars for which we find at least four different metal species, including one that is strongly Fe- and Ni-rich, indicative of the accretion of a planetesimal with core-Earth composition. We find one extremely massive (1.31 ± 0.01 M⊙) DA white dwarf showing weak Balmer lines, possibly indicating stellar magnetism. Another white dwarf shows strong Balmer line emission but no infrared excess, suggesting a low-mass sub-stellar companion. A high spectroscopic completeness (>99 per cent) has now been reached for Gaia DR2 sources within 40-pc sample, in the Northern hemisphere (δ > 0°) and located on the white dwarf cooling track in the Hertzsprung–Russell diagram. A statistical study of the full northern sample is presented in a companion paper.en
dc.format.mimetypeapplication/pdfpt_BR
dc.language.isoengpt_BR
dc.relation.ispartofMonthly notices of the royal astronomical society. Oxford. Vol. 497, no. 1 (Sep. 2020), p. 130-145pt_BR
dc.rightsOpen Accessen
dc.subjectStars: statisticsen
dc.subjectAnãs brancaspt_BR
dc.subjectPopulacoes estelarespt_BR
dc.subjectWhite dwarfsen
dc.subjectEstatística espacialpt_BR
dc.subjectSolar neighbourhooden
dc.titleGaia white dwarfs within 40 pc : I. Spectroscopic observations of new candidatespt_BR
dc.typeArtigo de periódicopt_BR
dc.identifier.nrb001120615pt_BR
dc.type.originEstrangeiropt_BR


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