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Detection of gravity modes in the massive binary V380 Cyg from Kepler space-based photometry and high-resolution spectroscopy


Based on Director's Discretionary Target (DDT) data gathered with NASA’s Discovery mission Kepler and with the HERMES spectrograph, installed at the Mercator telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias and supported by the Fund for Scientific Research of Flanders (FWO), Belgium, the Research Council of K. U. Leuven, Belgium, the Fonds National de la Recherche Scientific (F. R. S. – FNRS), Belgium, the Royal Observatory of Belgium, the Observatoire de Genève, Switzerland and the Thüringer Landessternwarte Tautenburg, Germany.



We report the discovery of low-amplitude gravity-mode oscillations in the massive binary star V380 Cyg, from 180 d of Kepler custom-aperture space photometry and 5 months of high-resolution high signal-to-noise ratio spectroscopy. The new data are of unprecedented quality and allowed the improvement of the orbital and fundamental parameters for this binary. The orbital solution was subtracted from the photometric data and led to the detection of periodic intrinsic variability with frequencies, of which some are multiples of the orbital frequency and others are not. Spectral disentangling allowed the detection of line-profile variability in the primary. With our discovery of intrinsic variability interpreted as gravity-mode oscillations, V380 Cyg becomes an important laboratory for future seismic tuning of the near-core physics in massive B-type stars.