Gaia white dwarfs within 40 pc - I. Spectroscopic observations of new candidates

Journal
Date Issued
2020
Author(s)
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.
•
•
Nitta, A.
•
Parsons, S. G.
•
Pelisoli, I.
•
Raddi, R.
•
Rebassa-Mansergas, A.
•
Ren, J. -J.
•
Schreiber, M. R.
•
•
Toloza, O.
•
Toonen, S.
•
Torres, S.
DOI
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 (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.
Volume
497
Issue
1
Start page
130
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2020MNRAS.497..130T
Rights
open.access
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