The eccentric massive binary V380 Cyg: revised orbital elements and interpretation of the intrinsic variability of the primary component

A. Tkachenko, P. Degroote, C. Aerts, K. Pavlovski, J. Southworth, P. I. Papics, E. Moravveji, V. Kolbas, V. Tsymbal, J. Debosscher, and K. Clemer

Institute of Astronomy, KU Leuven, Belgium

We present a detailed analysis and interpretation of the high-mass binary V380 Cyg, based on high-precision space photometry gathered with the Kepler space mission as well as high-resolution ground-based spectroscopy obtained with the HERMES spectrograph attached to the 1.2m Mercator telescope. We derive a precise orbital solution and the full physical properties of the system, including dynamical component mass estimates of 11.43+/-0.19 and 7.00+/-0.14 solar masses for the primary and secondary, respectively. Our frequency analysis reveals the rotation frequency of the primary in both the photometric and spectroscopic data and additional low amplitude stochastic variability at low frequency in the space photometry with characteristics that are compatible with recent theoretical predictions for gravity mode oscillations excited either by the convective core or by sub-surface convective layers. Doppler Imaging analysis of the silicon lines of the primary suggests the presence of two high-contrast stellar surface abundance spots which are located either at the same latitude or longitude. Comparison of the observed properties of the binary with present-day single-star evolutionary models shows that the latter are inadequate and lack a serious amount of near-core mixing.

Reference: Monthly Notices of the Royal Astronomical Society (MNRAS)
Status: Manuscript has been accepted