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The Toby Shake: Pulsations affected by precession and nutation in a close binary
Roy Østensen (Missouri State University), John Telting (Nordic Optical Telescope), Andrzej Baran (Krakow Pedagogical University), Mike Reed (Missouri State University)
The eclipsing sdb+dM binary KIC 9472174 = 2M1938+4603 is one of the few targets which was observed in short-cadence mode for the entire duration of the main Kepler mission. Its exceptionally complex pulsation spectrum contains periods ranging from around 200 seconds to 5 hours. The pulsation spectrum of both p-modes and g-modes has defied analysis by regular means due to the effects of fast rotation induced by the 0.25 d binary period. Analysing the entire Kepler dataset we have discovered strong amplitude modulation with a period of about 400 days in a majority of the pulsation modes, as well as more rapid modulations with a period of 39 days, which is associated with a strong frequency/phase modulation signal. A spectacular zoo of diverse modulation effects in amplitude and frequency/phase, some showing complete periodic phase inversion, may promise a new method for asteroseismic mode identification in close binaries.