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

Hambleton, K. M.; Kurtz, D. W.; Prša, A.; Guzik, J. A.; Pavlovski, K.; Bloemen, S.; Southworth, J.; Conroy, K.; Littlefair, S. P.; Fuller, J.

Abstract

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.

Citation

Hambleton, K. M., Kurtz, D. W., Prša, A., Guzik, J. A., Pavlovski, K., Bloemen, S., …Fuller, J. (2013). KIC 4544587: an eccentric, short-period binary system with δ Sct pulsations and tidally excited modes. Monthly Notices of the Royal Astronomical Society, 434(2), 925-940. https://doi.org/10.1093/mnras/stt886

• Journal Article Type: Article
• Acceptance Date: May 17, 2013
• Online Publication Date: Jul 17, 2013
• Publication Date: Sep 11, 2013
• Deposit Date: Jun 16, 2023
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 434
• Issue: 2
• Pages: 925-940
• DOI: https://doi.org/10.1093/mnras/stt886
• Keywords: Space and Planetary Science; Astronomy and Astrophysics; binaries: eclipsing, stars: individual: KIC 4544587, stars: oscillations, stars: variables: δ Scuti