During most of their life, stars fuse hydrogen into helium in their cores. The mixing of chemical elements in the radiative envelope of stars with a convective core is able to replenish the core with extra fuel. If effective, such deep mixing allows stars to live longer and change their evolutionary path. Yet localized observations to constrain internal mixing are absent so far. Gravity modes probe the deep stellar interior near the convective core and allow us to calibrate internal mixing processes. Here we provide core-to-surface mixing profiles inferred from observed dipole gravity modes in 26 rotating stars with masses between 3 and 10 solar masses. We find a wide range of internal mixing levels across the sample. Stellar models with stratified mixing profiles in the envelope reveal the best asteroseismic performance. Our results provide observational guidance for three-dimensional hydrodynamical simulations of transport processes in the deep interiors of stars.
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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
The iterative prewhitening code is freely available and documented at https://github.com/IvS-KULeuven/IvSPythonRepository. The stellar evolution code, MESA, is freely available and documented at http://mesa.sourceforge.net/. The stellar pulsation code, GYRE, is freely available and documented at https://bitbucket.org/rhdtownsend/gyre/wiki/Home.
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We thank the MESA and GYRE code developers for their efforts, public dissemination and training initiatives to make their software so accessible to the worldwide astrophysics community. We thank S. Ekström of the Geneva Observatory for providing mixing profiles from Georgy et al.4 in electronic format. We acknowledge the work of the teams behind the NASA Kepler and ESA Gaia space missions. This work is based on observations with the HERMES spectrograph at the Mercator Telescope, which is operated at La Palma, Spain, by the Flemish Community. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France, and NASA’s Astrophysics Data System. The research leading to these results has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement number 670519: MAMSIE), from the National Science Foundation (grant number NSF PHY-1748958), from the KU Leuven Research Council (grant number C16/18/005: PARADISE) and from the Research Foundation Flanders (FWO) by means of PhD Fellowships to M.M. and S. Gebruers under contract numbers 11F7120N and 11E5620N and a senior post-doctoral fellowship to D.M.B. under grant agreement number 1286521N. Funding for the Kepler Mission was provided by NASA’s Science Mission Directorate. Gaia data are being processed by the Gaia Data Processing and Analysis Consortium (DPAC); funding for the DPAC is provided by national institutions, in particular the institutions participating in the Gaia MultiLateral Agreement (MLA).
The authors declare no competing interests.
Peer review information Nature Astronomy thanks Joyce Guzik, Ernst Paunzen and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Pedersen, M.G., Aerts, C., Pápics, P.I. et al. Internal mixing of rotating stars inferred from dipole gravity modes. Nat Astron 5, 715–722 (2021). https://doi.org/10.1038/s41550-021-01351-x
The Astronomy and Astrophysics Review (2021)