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 highresolution 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 M ⊙ 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.

The eclipsing and double-lined spectroscopic binary V380 Cyg is an extremely important probe of stellar evolution: its primary component is a high-mass star at the brink of leaving the main sequence whereas the secondary star is still in the early part of its main sequence lifetime. We present extensive high-resolutionéchelle and grating spectroscopy from Ondřejov, Calar Alto, Victoria and La Palma. We apply spectral disentangling to unveil the individual spectra of the two stars and obtain new spectroscopic elements. The secondary star contributes only about 6 per cent of the total light, which remains the main limitation to measuring the system's characteristics. We determine improved physical properties, finding masses 13.1 ± 0.3 and 7.8 ± 0.1 M , radii 16.2 ± 0.3 and 4.06 ± 0.08 R , and effective temperatures 21 750 ± 280 and 21 600 ± 550 K, for the primary and secondary components, respectively. We perform a detailed abundance analysis by fitting non-local thermodynamic equilibrium (LTE) theoretical line profiles to the disentangled spectrum of the evolved primary star, and reveal an elemental abundance pattern reminiscent of a typical nearby B star. Contrary to the predictions of recent theoretical evolution models with rotational mixing, no trace of abundance modifications due to the CNO cycle are detected. No match can be found between the predictions of these models and the properties of the primary star: a mass discrepancy of 1.5 M exists and remains unexplained.

Algol (β Persei) is the prototypical semi-detached eclipsing binary and a hierarchical triple system. From 2006 to 2010 we obtained 121 high-resolution and high-S/Néchelle spectra of this object. Spectral disentangling yields the individual spectra of all three stars, and greatly improved elements both the inner and outer orbits. We find masses of M A = 3.39 ± 0.06 M ⊙ , M B = 0.770 ± 0.009 M ⊙ and M C = 1.58 ± 0.09 M ⊙ . The disentangled spectra also give the light ratios between the components in the B and V bands. Atmospheric parameters for the three stars are determined, including detailed elemental abundances for Algol A and Algol C. We find the following effective temperatures: T A = 12 550 ± 120 K, T B = 4900 ± 300 K and T C = 7550 ± 250 K. The projected rotational velocities are v A sin i A = 50.8 ± 0.8 km s −1 , v B sin i B = 62±2 km s −1 and v C sin i C = 12.4±0.6 km s −1 . This is the first measurement of the rotational velocity for Algol B, and confirms that it is synchronous with the orbital motion. The abundance patterns of components A and C are identical to within the measurement errors, and are basically solar. They can be summarised as mean metal abundances: [M/H] A = −0.03 ± 0.08 and [M/H] C = 0.04 ± 0.09. A carbon deficiency is confirmed for Algol A, with tentative indications for a slight overabundance of nitrogen. The ratio of their abundances is (C/N) A = 2.0 ± 0.4, half of the solar value of (C/N) ⊙ = 4.0 ± 0.7. The new results derived in this study, including detailed abundances and metallicities, will enable tight constraints on theoretical evolutionary models for this complex system.

The chemical composition of stellar photospheres in mass-transferring binary systems is a precious diagnostic of the nucleosynthesis processes that occur deep within stars, and preserves information on the components' history. The binary system u Her belongs to a group of hot Algols with both components being B-stars. We have isolated the individual spectra of the two components by the technique of spectral disentangling of a new series of 43 high-resolutioń echelle spectra. Augmenting these with an analysis of the Hipparcos photometry of the system yields revised stellar quantities for the components of u Her. For the primary component (the mass-gaining star) we find M A = 7.88 ± 0.26 M ⊙ , R A = 4.93 ± 0.15 R ⊙ and T eff,A = 21 600 ± 220 K. For the secondary (the mass-losing star) we find M B = 2.79 ± 0.12 M ⊙ , R B = 4.26 ± 0.06 R ⊙ and T eff,B = 12 600 ± 550 K. A non-LTE analysis of the primary star's atmosphere reveals deviations in the abundances of nitrogen and carbon from the standard cosmic abundance pattern in accord with theoretical expectations for CNO nucleosynthesis processing. From a grid of calculated evolutionary models the best match to the observed properties of the stars in u Her enabled tracing the initial properties and history of this binary system. We confirm that it has evolved according to case A mass transfer. A detailed abundance analysis of the primary star gives C/N = 0.9, which supports the evolutionary calculations and indicates strong mixing in the early evolution of the secondary component, which was originally the more massive of the two. The composition of the secondary component would be a further important constraint on the initial properties of u Her system, but requires spectra of a higher signal to noise ratio.

KIC 8560861 (HD 183648) is a marginally eccentric (e = 0.05) eclipsing binary with an orbital period of P orb = 31.973 d, exhibiting mmag amplitude pulsations on time scales of a few days. We present the results of the complex analysis of high and medium-resolution spectroscopic data and Kepler Q0 -Q16 long cadence photometry. The iterative combination of spectral disentangling, atmospheric analysis, radial velocity and eclipse timing variation studies, separation of pulsational features of the light curve, and binary light curve analysis led to the accurate determination of the fundamental stellar parameters. We found that the binary is composed of two main sequence stars with an age of 0.9 ± 0.2 Gyr, having masses, radii and temperatures of M 1 = 1.93 ± 0.12 M ⊙ , R 1 = 3.30 ± 0.07 R ⊙ , T eff1 = 7650 ± 100 K for the primary, and M 2 = 1.06 ± 0.08 M ⊙ , R 2 = 1.11 ± 0.03 R ⊙ , T eff2 = 6450 ± 100 K for the secondary. After subtracting the binary model, we found three independent frequencies, two of which are separated by twice the orbital frequency. We also found an enigmatic half orbital period sinusoidal variation that we attribute to an anomalous ellipsoidal effect. Both of these observations indicate that tidal effects are strongly influencing the luminosity variations of HD 183648. The analysis of the eclipse timing variations revealed both a parabolic trend, and apsidal motion with a period of P obs apse = 10 400 ± 3 000 y, which is three times faster than what is theoretically expected. These findings might indicate the presence of a distant, unseen companion.