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

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 y per cycle. The primary and secondary components of KIC 4544587 reside within the δ Scuti and γ Dor instability region of the Hurtzsprung-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 KPNO, the fundamental parameters of this important system have been determined, including the stellar masses, 1.98 ±0.07 M ⊙ and 1.60 ± 0.06 M ⊙ , and radii, 1.76 ± 0.03 R ⊙ 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 infact 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.

Keplerdetection of a new extreme planetary system orbiting the subdwarf-B pulsator KIC 10001893

“…3) 3 . Although tidally excited pulsations have already been observed in other stars (e.g., Hambleton et al 2013), this is the first time that we have a clear indication of this phenomenon in an sdB star.…”

Pulsating red giant stars in eccentric binary systems discovered fromKeplerspace-based photometry

“…The first such object discovered to confirm the theory was KOI 54 (HD 187091, Welsh et al 2011). Subsequently, more tidally interacting eccentric binary systems have been discovered in the Kepler field as well as in the Magellanic clouds from OGLE observations by Thompson et al (2012), Hambleton et al (2013) and Nicholls & Wood (2012), respectively. Only observations from Kepler provide the temporal resolution to allow for a dedicated seismic analysis for these stars.…”

Light Curve Solutions of Ten Eccentric Kepler Binaries, Three of them with Tidally Induced Humps

“…Hence, the 'apsidal motion test' could be used as a probe of stellar internal structure if precise values of global parameters are available (Claret & Gimenez 2010). There are important recent studies of this effect based on the observed apsidal motion of double-lined binaries (Lacy et al 2015;Zasche et al 2014;Bulut, Bulut, & Cicek 2014;Garcia et al 2014;Kozyreva & Kusakin 2014;Harmanec et al 2014;Wilson & Van Hamme 2014;Hambleton et al 2013;Wolf et al 2013;Claret 2012;Zasche 2012;Kuznetsov et al 2011;Claret & Gimenez 2010;Wolf et al 2010;Gimenez & Quintana 1992;Barembaum & Etzel 1995;etc. ) .…”

“…(5) Initially the primary temperature T 1 was fixed to be equal to the mean target temperature T m ( Table 1) that has been estimated using dedicated pre-launch groundbased optical multi-colour photometry plus Two Micron All Sky Survey (2MASS) J, K, and H magnitudes (Prsa et al 2011). Our procedure of the light curve solutions was quite similar to that of Hambleton et al (2013) and was carried out in several stages.…”