Gaia reveals evidence for merged white dwarfs

Mukremin Kilic, N. C. Hambly, P. Bergeron, C. Genest-Beaulieu, N. Rowell

Research output: Contribution to journalArticlepeer-review

Abstract

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.
Original languageEnglish
Pages (from-to)L113–L117
JournalMonthly Notices of the Royal Astronomical Society: Letters
Volume479
Issue number1
Early online date18 Jun 2018
DOIs
Publication statusPublished - 1 Sep 2018

Keywords

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

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