Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 479, Issue 1, Pages L113-L117Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnrasl/sly110
Keywords
stars: evolution; stars: fundamental parameters; Hertzsprung-Russell and colour-magnitude diagrams; white dwarfs; Galaxy: disc; Galaxy: stellar content
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Funding
- NASA [NNX14AF65G]
- NSERC Canada
- Fund FRQ-NT (Quebec)
- NASA [NNX14AF65G, 684557] Funding Source: Federal RePORTER
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We use Gaia Data Release 2 to identify 13 928 white dwarfs (WDs) within 100 pc of the Sun. The exquisite astrometry from Gaia reveals for the first time a bifurcation in the observed WD sequence in both Gaia and the Sloan Digital Sky Survey (SDSS) passbands. The latter is easily explained by a helium atmosphere WD fraction of 36 per cent. However, the bifurcation in the Gaia colour-magnitude diagram depends on both the atmospheric composition and the mass distribution. We simulate theoretical colour-magnitude diagrams for single and binary WDs using a population synthesis approach and demonstrate that there is a significant contribution from relatively massive WDs that likely formed through mergers. These include WD remnants of main-sequence (blue stragglers) and post-main-sequence mergers. The mass distribution of the SDSS subsample, including the spectroscopically confirmed WDs, also shows this massive bump. This is the first direct detection of such a population in a volume-limited sample.
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