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arXiv · 1805.01227

Gaia Reveals Evidence for Merged White Dwarfs

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

We use Gaia Data Release 2 to identify 13,928 white dwarfs within 100 pc of the Sun. The exquisite astrometry from Gaia reveals for the first time a bifurcation in the observed white dwarf sequence in both Gaia and the Sloan Digital Sky Survey (SDSS) passbands. The latter is easily explained by a helium atmosphere white dwarf fraction of 36%. 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 white dwarfs using a population synthesis approach and demonstrate that there is a significant contribution from relatively massive white dwarfs that likely formed through mergers. These include white dwarf remnants of main-sequence (blue stragglers) and post-main sequence mergers. The mass distribution of the SDSS subsample, including the spectroscopically confirmed white dwarfs, also shows this massive bump. This is the first direct detection of such a population in a volume-limited sample.

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Mukremin Kilic, N. C. Hambly, P. Bergeron, C. Genest-Beaulieu, N. Rowell. 2018-05-03. Gaia Reveals Evidence for Merged White Dwarfs. https://doi.org/10.1093/mnrasl/sly110

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