Year: 2023
Type: article
Abstract: Type Ia supernovae are cosmic distance indicators1,2, and the main source of iron in the Universe3,4, but their formation paths are still debated. Several dozen supersoft X-ray sources, in which a white dwarf accretes hydrogen-rich matter from a non-degenerate donor star, have been observed5 and suggested as Type Ia supernovae progenitors6–9. However, observational evidence for hydrogen, which is expected to be stripped off the donor star during the supernova explosion10, is lacking. Helium-accreting white dwarfs, which would circumvent this problem, have been predicted for more than 30 years (refs. 7,11,12), including their appearance as supersoft X-ray sources, but have so far escaped detection. Here we report a supersoft X-ray source with an accretion disk whose optical spectrum is completely dominated by helium, suggesting that the donor star is hydrogen-free. We interpret the luminous and supersoft X-rays as resulting from helium burning near the surface of the accreting white dwarf. The properties of our system provide evidence for extended pathways towards Chandrasekhar-mass explosions based on helium accretion, in particular for stable burning in white dwarfs at lower accretion rates than expected so far. This may allow us to recover the population of the sub-energetic so-called Type Iax supernovae, up to 30% of all Type Ia supernovae13, within this scenario.
Source: Nature
Institutions: Max Planck Institute for Extraterrestrial Physics, University of Bonn, Max Planck Institute for Radio Astronomy, European Southern Observatory, University of Cape Town, University of the Free State, South African Astronomical Observatory, University of Warsaw, Max Planck Institute for Astrophysics, University of Tübingen, Centre National de la Recherche Scientifique, Observatoire astronomique de Strasbourg, Université de Strasbourg, Massachusetts Institute of Technology
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $11,690
Funders: National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, Australian National University, Deutsche Forschungsgemeinschaft, Eberhard Karls Universität Tübingen, Max-Planck-Gesellschaft, Universität Hamburg, Rheinische Friedrich-Wilhelms-Universität Bonn, Leibniz-Institut für Astrophysik Potsdam, Ames Research Center, Science Mission Directorate, Leibniz-Gemeinschaft, Russian Academy of Sciences, Lawrence Livermore National Laboratory
OpenAlex ID: W4353055701