期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 497, 期 1, 页码 130-145出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/staa1892
关键词
stars: statistics; white dwarfs; solar neighbourhood
资金
- European Research Council under the European Union [677706]
- UK STFC [ST/P000495, ST/T000406/1]
- MINECO under the Ramon y Cajal programme [RYC-2016-20254]
- AGAUR grant [SGR-661/2017]
- Fondecyt [1181404]
- ASI-INAF [I/037/12/0, 2017-14-H.0]
- INAF INAF main streams [43/2018]
- postdoctoral fellowship programme Beatriu de Pinos
- Government of Catalonia
- Horizon 2020 programme of research and innovation of the European Union under the Maria Sklodowska-Curie grant [801370]
- [AYA2017-86274-P]
- STFC [ST/T000406/1, ST/R003424/1] Funding Source: UKRI
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-circle dot) 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 (delta > 0 degrees) 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.
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