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KIC 9246715: The Double Red Giant Eclipsing Binary With Odd Oscillations
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  • Meredith L. RawlsOrcid,
  • patrick gaulme,
  • Jean McKeever,
  • Jason Jackiewicz,
  • Jerome A. Orosz,
  • Enrico Corsaro,
  • Paul Beck,
  • Awaiting Activation,
  • David Latham,
  • Christian Latham
Meredith L. Rawls
Orcid
New Mexico State University
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patrick gaulme
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Jean McKeever
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Jason Jackiewicz
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Jerome A. Orosz
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Enrico Corsaro
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Awaiting Activation
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David Latham
Harvard-Smithsonian Center for Astrophysics (CFA)
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Christian Latham
Harvard-Smithsonian Center for Astrophysics (CFA)
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Abstract

We combine Kepler photometry with ground-based spectra to present a comprehensive dynamical model of the double red giant eclipsing binary KIC 9246715. While the two stars are very similar in mass (\(M_{1}=2.171\begin{subarray}{c}+0.006\\ -0.008\end{subarray}\ M_{\odot}\), \(M_{2}=2.149\begin{subarray}{c}+0.006\\ -0.008\end{subarray}\ M_{\odot}\)) and radius (\(R_{1}=8.37\begin{subarray}{c}+0.03\\ -0.07\end{subarray}\ R_{\odot}\), \(R_{2}=8.30\begin{subarray}{c}+0.04\\ -0.03\end{subarray}\ R_{\odot}\)), an asteroseismic analysis finds one main set of solar-like oscillations with unusually low-amplitude, wide modes. A second set of oscillations from the other star may exist, but this marginal detection is extremely faint. Because the two stars are nearly twins, KIC 9246715 is a difficult target for a precise test of the asteroseismic scaling relations, which yield \(M=2.17\pm 0.14\ M_{\odot}\) and \(R=8.26\pm 0.18\ R_{\odot}\). Both stars are consistent with the inferred asteroseismic properties, but we suspect the main oscillator is Star 2 because it is less active than Star 1. We find evidence for stellar activity and modest tidal forces acting over the 171-day eccentric orbit, which are likely responsible for the essential lack of solar-like oscillations in one star and weak oscillations in the other. Mixed modes indicate the main oscillating star is on the secondary red clump (a core-He-burning star), and stellar evolution modeling supports this with a coeval history for a pair of red clump stars. This system is a useful case study and paves the way for a detailed analysis of more red giants in eclipsing binaries, an important benchmark for asteroseismology.