Presence of mixed modes in red giants in binary systems
Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077, Göttingen, DE
2 Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000, Aarhus C, DK
3 Institute for Astrophysics, Georg-August University Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen DE
4 School of Physics and Astronomy, U. Birmingham, Edgbaston, Birmingham, B15 2TT, UK
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Published online: 27 October 2017
The frequencies of oscillation modes in stars contain valueable information about the stellar properties. In red giants the frequency spectrum also contains mixed modes, with both pressure (p) and gravity (g) as restoring force, which are key to understanding the physical conditions in the stellar core. We observe a high fraction of red giants in binary systems, for which g-dominated mixed modes are not pronounced. This trend leads us to investigate whether this is specific for binary systems or a more general feature. We do so by comparing the fraction of stars with only p-dominated mixed modes in binaries and in a larger set of stars from the APOKASC sample. We find only p-dominated mixed modes in about 50% of red giants in detached eclipsing binaries compared to about 4% in the large sample. This could indicate that this phenomenon is tightly related to binarity and that the binary fraction in the APOKASC sample is about 8%.
© Owned by the authors, published by EDP Sciences, 2017
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