KOI-54: THE KEPLER DISCOVERY OF TIDALLY EXCITED PULSATIONS AND BRIGHTENINGS IN A HIGHLY ECCENTRIC BINARY

By W. Welsh, J. Orosz, C. Aerts, T. Brown, E. Brugamyer, W. Cochran, R. Gilliland, J. Guzik, D. Kurtz, D. Latham and 20 more. 2011

172 citations recorded by the source corpus.

Kepler observations of the star HD 187091 (KIC 8112039, hereafter KOI-54) revealed a remarkable light curve exhibiting sharp periodic brightening events every 41.8 days with a superimposed set of oscillations forming a beating pattern in phase with the brightenings. Spectroscopic observations revealed that this is a binary star with a highly eccentric orbit, e = 0.83. We are able to match the Kepler light curve and radial velocities with a nearly face-on (i = 5.°5) binary star model in which the brightening events are caused by tidal distortion and irradiation of nearly identical A stars during their close periastron passage. The two dominant oscillations in the light curve, responsible for the beating pattern, have frequencies that are the 91st and 90th harmonic of the orbital frequency. The power spectrum of the light curve, after removing the binary star brightening component, reveals a large number of pulsations, 30 of which have a signal-to-noise ratio ≳7. Nearly all of these pulsations have frequencies that are either integer multiples of the orbital frequency or are tidally split multiples of the orbital frequency. This pattern of frequencies unambiguously establishes the pulsations as resonances between the dynamic tides at periastron and the free oscillation modes of one or both of the stars. KOI-54 is only the fourth star to show such a phenomenon and is by far the richest in terms of excited modes.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/39d7d3703fd1b54e2d1187e964ad900dfcf27b45

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Citations in the corpus

KEPLER MISSION STELLAR AND INSTRUMENT NOISE PROPERTIES (2011, background): “…Kepler has revealed a remarkable eccentric A-star binary viewed nearly face on with reflected light features superimposed on tidally-forced g-mode oscillations (Welsh et al. 2011), and two instances of mutually eclipsing hierarchical triple systems (Carter et al. 2011; Derekas et al. 2011).”
KEPLER ECLIPSING BINARY STARS. VII. THE CATALOG OF ECLIPSING BINARIES FOUND IN THE ENTIRE KEPLER DATA SET (2015, background): “However, this effect is temperature dependent and so for objects with hotter components that both contribute significantly to the flux, as in the case of KOI-54 (Welsh et al. 2011), which contains two A stars, the irradiation contributes notably to the light curve (approximatly half of the amplitude”
Tidal Dissipation in Stars and Giant Planets (2014, background): “A particularly interesting example is KOI-54 (HD 187091) (Welsh et al. 2011, who also mention three pre-Kepler cases).”
Dawes Review 6: The Impact of Companions on Stellar Evolution (2016, methodology): “Primary distorted at periastron Welsh et al. 2011 Chemically peculiar stars Barium stars Single stars that accrete wind from a Ba-rich, AGB companion ([Fe/H] ∼ 0) Merle et al. 2016 CH/dwarf C stars Single stars that accrete wind from a C-rich AGB companion ([Fe/H] ∼ −1) Jorissen et al. 2016 CEMP…”
KEPLER ECLIPSING BINARY STARS. III. CLASSIFICATION OF KEPLER ECLIPSING BINARY LIGHT CURVES WITH LOCALLY LINEAR EMBEDDING (2012, methodology): “A set of 2165 EBs has been identified and made available via two data releases (Prša et al. 2011; Slawson et al. 2011, parts I and II, respectively) and quite a few papers studied individual Kepler EBs (e.g., Southworth et al. 2011; Steffen et al. 2011; Welsh et al. 2011; Winn et al. 2011).”
TESS Eclipsing Binary Stars. I. Short-cadence Observations of 4584 Eclipsing Binaries in Sectors 1–26 (2021, background): “A handful of them have been studied in detail (Welsh et al. 2011; Hambleton et al. 2013, 2016, 2018; Shporer et al. 2016; Fuller et al. 2017; Guo et al. 2017, 2019).”