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Deviations from a uniform period spacing of gravity modes in a massive star

Nature volume 464, pages 259–261 (2010)Cite this article

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Abstract

The life of a star is dominantly determined by the physical processes in the stellar interior. Unfortunately, we still have a poor understanding of how the stellar gas mixes near the stellar core, preventing precise predictions of stellar evolution1. The unknown nature of the mixing processes as well as the extent of the central mixed region is particularly problematic for massive stars2. Oscillations in stars with masses a few times that of the Sun offer a unique opportunity to disentangle the nature of various mixing processes, through the distinct signature they leave on period spacings in the gravity mode spectrum3. Here we report the detection of numerous gravity modes in a young star with a mass of about seven solar masses. The mean period spacing allows us to estimate the extent of the convective core, and the clear periodic deviation from the mean constrains the location of the chemical transition zone to be at about 10 per cent of the radius and rules out a clear-cut profile.

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Figure 1: The light curve of HD 50230 measured by the CoRoT satellite.
Figure 2: Extracted frequency spectrum in the g mode region.
Figure 3: The components and values of the g mode period spacing.
Figure 4: The influence of the size of the convective mixing region on the mean value of the period spacing.

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Acknowledgements

The research leading to these results received funding from the European Research Council under the European Community's Seventh Framework Programme (PROSPERITY), from the Research Council of KU Leuven and from the Belgian Federal Science Policy. The CoRoT space mission has been developed, and is operated by, CNES, with contributions from Austria, Belgium, Brazil, ESA, Germany and Spain.

Author Contributions P.D. and C.A. analysed and interpreted the light curve; M.B., A.M., A.N. and J.M. computed theoretical models; P.D., M.B. and E.N. analysed spectroscopic data; S.B., R.O., M.V. and K.S. made spectroscopic observations; and A.B., M.A., F.B., C.C. and E.M. are the CoRoT instrument builders.

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Authors and Affiliations

  1. Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium ,

    Pieter Degroote, Conny Aerts, Maryline Briquet, Steven Bloemen, Raquel Oreiro, Maja Vučković & Kristof Smolders

  2. Department of Astrophysics, IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands,

    Conny Aerts

  3. LESIA, UMR8109, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, 92195 Meudon, France ,

    Annie Baglin, Michel Auvergne, Claude Catala & Eric Michel

  4. Institut d'Astrophysique et de Géophysique de l'Université de Liege, Allée du 6 Aout 17, 4000 Liege, Belgium ,

    Andrea Miglio, Arlette Noels & Josefina Montalban

  5. Astronomical Institute, Wroclaw University, Kopernika 11, 51-622 Wroclaw, Poland ,

    Ewa Niemczura

  6. Institut d'Astrophysique Spatiale (IAS), Batiment 121, F-91405, Orsay Cedex, France ,

    Frederic Baudin

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  1. Pieter Degroote
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Correspondence to Pieter Degroote.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This document describes in more detail the determination of the fundamental parameters, the frequency analysis and the period spacing extraction. It contains 3 supplementary figures, illustrating the determination of the fundamental parameters of the star, and providing an overview of the frequency content of the CoRoT light curve. A list of references relevant for the supplementary information only is added. (PDF 613 kb)

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Degroote, P., Aerts, C., Baglin, A. et al. Deviations from a uniform period spacing of gravity modes in a massive star. Nature 464, 259–261 (2010). https://doi.org/10.1038/nature08864

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