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The origin of hypervelocity white dwarfs in the merger disruption of He–C–O white dwarfs

Nature Astronomy (2025)Cite this article

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Abstract

Hypervelocity white dwarfs (HVWDs) are stellar remnants moving at speeds that exceed the Milky Way’s escape velocity. The origins of the fastest HVWDs are enigmatic, with proposed formation scenarios struggling to explain both their extreme velocities and observed properties. Here we report a three-dimensional hydrodynamic simulation of a merger between two hybrid helium–carbon–oxygen WDs (with masses of 0.69 M⊙ and 0.62 M⊙, where M⊙ is the mass of the Sun). We find that the merger leads to a partial disruption of the secondary WD, coupled with a double-detonation explosion of the primary WD. This launches the remnant core of the secondary WD at a speed of 2,000 km s−1, consistent with observed HVWDs. The low mass of the ejected remnant and heating from the primary WD’s ejecta explain the observed luminosities and temperatures of hot HVWDs, which are otherwise difficult to reconcile with previous models (such as the dynamically driven double-degenerate double-detonation scenario). This discovery establishes a new formation channel for HVWDs and points to a pathway for producing peculiar type Ia supernovae and faint explosive transients.

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Fig. 1: WD disruption and shock propagation.
Fig. 2: Production of radioactive elements during the merger.
Fig. 3: Evolution of the MESA model and comparison with HVWD observations.

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Data availability

The MESA input files for relaxation, heating and evolution are available via Zenodo at https://doi.org/10.5281/zenodo.15700950 (ref. 46). All data underlying this research that are not in the Zenodo repository (particularly the many hydrodynamical simulation snapshots that are too large) are available upon reasonable request from the corresponding authors. Source data are provided with this paper.

Code availability

We made use of the AREPO30,41,43,47, MESA36,44,45,48, Matplotlib49, NumPy50 and SciPy51 codes. MESA inlists are available through the MESA community on Zenodo at https://doi.org/10.5281/zenodo.15700950 (ref. 46).

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Acknowledgements

H.B.P. acknowledges support for this project from the European Union’s Horizon 2020 research and innovation programme under grant agreement number 865932-ERC-SNeX. H.G. acknowledges support for the project from the Council for Higher Education of Israel. A.B. was supported by the Deutsche Forschungsgemeinschaft (DFG) through grant number GE2506/18-1 and by the Kavli Summer Program, which took place at MPA in Garching in July 2023 and was supported by the Kavli Foundation. We thank E. Bauer and R. Fisher for their valuable comments and discussions.

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Author notes

  1. These authors contributed equally: Hila Glanz, Hagai B. Perets.

Authors and Affiliations

  1. Technion–Israel Institute of Technology, Haifa, Israel

    Hila Glanz & Hagai B. Perets

  2. Institut für Physik und Astronomie, Universität Potsdam, Potsdam, Germany

    Aakash Bhat

  3. Dr. Karl-Remeis Observatory, Bamberg, Germany

    Aakash Bhat

  4. Max-Planck-Institut für Astrophysik, Garching, Germany

    Ruediger Pakmor

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  1. Hila Glanz
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Contributions

H.G. led the key research, ran the hydrodynamical simulations and analysed the results. H.B.P. initiated and supervised the project, suggested the main ideas, analysed the results and wrote the main parts of the paper. A.B. ran the long-term WD evolution modelling and analysis. R.P. assisted with running the hydrodynamical simulations. All authors contributed to writing the paper, making the figures and reviewing the manuscript.

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Correspondence to Hila Glanz or Hagai B. Perets.

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Supplementary information

Supplementary Figs. 1–3, Tables 1–3 and Sections 2.1–2.6.

Supplementary Video 1

Simulation video. Showing slices of the different densities and temperature and presenting the beginning of the mass transfer, the disruption of the secondary during the interaction, the double detonation and the ejection of the HVWD.

Source data

Source Data Fig. 2

Full data behind Fig. 2.

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Glanz, H., Perets, H.B., Bhat, A. et al. The origin of hypervelocity white dwarfs in the merger disruption of He–C–O white dwarfs. Nat Astron (2025). https://doi.org/10.1038/s41550-025-02633-4

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