Gaia white dwarfs within 40 pc – I. Spectroscopic observations of new candidates. Issue 1 (2nd July 2020)

• Record Type: Journal Article
• Authors: Tremblay, P-E; Hollands, M A; Gentile Fusillo, N P; McCleery, J; Izquierdo, P; Gänsicke, B T; Cukanovaite, E; Koester, D; Brown, W R; Charpinet, S; Cunningham, T; Farihi, J; Giammichele, N; van Grootel, V; Hermes, J J; Hoskin, M J; Jordan, S; Kepler, S O; Kleinman, S J; Manser, C J; Marsh, T R; de Martino, D; Nitta, A; Parsons, S G; Pelisoli, I; Raddi, R; Rebassa-Mansergas, A; Ren, J-J; Schreiber, M R; Silvotti, R; Toloza, O; Toonen, S; Torres, S;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 497:Issue 1(2020)
• Page Start: 130
• Page End: 145
• Publication Date: 2020-07-02
• Subjects: stars: statistics -- white dwarfs -- solar neighbourhood; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa1892
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We 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 (〈 T eff 〉 = 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.