Year: 2026
Type: preprint
Abstract: Open clusters are powerful laboratories for investigating the formation and evolution of white dwarfs (WDs), as their well-constrained ages link WDs to their progenitor stars. This is particularly valuable for atypical WDs, including magnetic WDs and those with non-hydrogen-dominated spectra, whose origins can be difficult to disentangle in the field. We assemble the largest sample to date of atypical WDs in open clusters: eight non-magnetic WDs with helium-dominated spectra, five with featureless spectra, and five magnetic WDs showing hydrogen or helium lines. We find no significant difference between the initial--final mass relations of hydrogen- and helium-atmosphere WDs, nor robust spatial or kinematic differences. The strongest difference from the field is a deficit of non-DAs between $0.8$ and $1.0\,\mathrm{M}_\odot$, where the field predicts $6.0^{+0.8}_{-0.7}$ WDs, yet none are observed, with a probability of only $0.37\%$. Massive magnetic WDs show a similar deficit: only one of 20 cluster WDs with $M_{\mathrm{WD}}\geq1.0\,\mathrm{M}_\odot$ and $T_{\mathrm{eff}}\geq20{,}000\,{\rm K}$ is magnetic, compared with 10 of 16 in the field. Together, these deficits are consistent with an additional field population of massive merger remnants, particularly high-mass magnetic WDs and warm/hot DQs. Such objects may be underrepresented in clusters because young systems provide limited time for certain classes of delayed mergers, while older clusters lose members or dissolve; the field accumulates binary evolution products over Galactic timescales. Magnetic cluster WDs consistent with single-star evolution further suggest mass-dependent magnetic-field emergence, with fields appearing early in some massive WDs while young lower-mass WDs remain consistent with delayed emergence.
Source: arXiv (Cornell University)
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, Gordon and Betty Moore Foundation, Yale University, Carnegie Institution of Washington, Ohio State University, California Institute of Technology, Harvard University, Johns Hopkins University, New Mexico State University, Australian National Data Service, National Computational Infrastructure, Astronomy Australia Limited, Space Telescope Science Institute, Australian Government, European Space Agency, Flatiron Health, European Commission, Queen's University Belfast, Australian National University, Durham University, École Polytechnique Fédérale de Lausanne, Monash University, Swinburne University of Technology, Curtin University of Technology, University of Toronto, National Central University, Universidad Nacional Autónoma de México, Yunnan University, Nanjing University, Eötvös Loránd Tudományegyetem, China National Textile and Apparel Council, Leibniz-Institut für Astrophysik Potsdam, Max-Planck-Institut für Astronomie, University of Illinois at Urbana-Champaign, University of Colorado Boulder, Smithsonian Astrophysical Observatory, Science Mission Directorate, Natural Sciences and Engineering Research Council of Canada, Leibniz-Gemeinschaft, Australian Astronomical Optics-Macquarie, National Astronomical Observatories, Chinese Academy of Sciences, National Cancer Institute, Planetary Science Division, Los Alamos National Laboratory
OpenAlex ID: W7221188901