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Published September 11, 2013 | Published + Accepted Version
Journal Article Open

KIC 4544587: an eccentric, short-period binary system with δ Sct pulsations and tidally excited modes


We present Kepler photometry and ground-based spectroscopy of KIC 4544587, a short-period eccentric eclipsing binary system with self-excited pressure and gravity modes, tidally excited modes, tidally influenced p modes and rapid apsidal motion of 182 yr per cycle. The primary and secondary components of KIC 4544587 reside within the δ Scuti and γ Dor instability region of the Hertzsprung–Russell diagram, respectively. By applying the binary modelling software PHOEBE to prewhitened Kepler photometric data and radial velocity data obtained using the William Herschel Telescope and 4-m Mayall telescope at Kitt Peak Northern Observatory (KPNO), the fundamental parameters of this important system have been determined, including the stellar masses, 1.98 ±0.07 and 1.60 ± 0.06  M_⊙, and radii, 1.76 ± 0.03 and 1.42 ± 0.02 R_⊙, for the primary and secondary components, respectively. Frequency analysis of the residual data revealed 31 modes, 14 in the gravity mode region and 17 in the pressure mode region. Of the 14 gravity modes, 8 are orbital harmonics: a signature of tidal resonance. While the measured amplitude of these modes may be partially attributed to residual signal from binary model subtraction, we demonstrate through consideration of the folded light curve that these frequencies do in fact correspond to tidally excited pulsations. Furthermore, we present an echelle diagram of the pressure mode frequency region (modulo the orbital frequency) and demonstrate that the tides are also influencing the p modes. A first look at asteroseismology hints that the secondary component is responsible for the p modes, which is contrary to our expectation that the hotter star should pulsate in higher radial overtone, higher frequency p modes.

Additional Information

© 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2013 May 17. Received 2013 May 15; in original form 2012 September 3. We express our sincere thanks to NASA and the Kepler team for allowing us to work with and analyse the Kepler data, making this work possible. The Kepler mission is funded by NASA's Science Mission Directorate. This work was also supported by the Science and Technology Funding Council (STFC). We would also like to thank the RAS for providing grants which enabled KH's attendance at conferences and thus enabled the development of collaborations and the successful completion of this work. AP acknowledges support through NASA Kepler PSP grant NNX12AD20G. The research leading to these results has received funding from the European Research Council under the European Community's Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement no. 227224 (PROSPERITY), as well as from the Research Council of KU Leuven grant agreement GOA/2008/04. We acknowledge the observations taken using the 4-m Mayall telescope at the NOAO, survey number #11A-0022 and the Isaac Newton Group of Telescopes for the use of the William Herschel Telescope (WHT). The WHT is operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. We would also like to thank Susan Thompson and William Welsh for their comments and suggestions.

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Accepted Version - 1306.1819.pdf


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