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Gaia reveals evidence for merged white dwarfs

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Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
Publication statusPublished - 1 Sep 2018


We use Gaia Data Release 2 to identify 13 928 white dwarfs (WDs) within100 pc of the Sun. The exquisite astrometry from Gaia reveals for thefirst 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 asignificant 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 apopulation in a volume-limited sample.

    Research areas

  • stars: evolution, stars: fundamental parameters, Hertzsprung-Russell and colour-magnitude diagrams, white dwarfs, Galaxy: disc, Galaxy: stellar content

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