Context. The influence of binarity on the late stages of stellar evolution remains an open issue. Aims. While the first binary post-AGB stars were serendipitously discovered, the distinct characteristics of their spectral energy distribution (SED) allowed us to launch a more systematic search for binaries. We selected post-AGB objects, which exhibit a broad dust excess starting either at H or K, pointing to the presence of a gravitationally bound dusty disc in the system. We initiated an extensive multiwavelength study of those systems and here report on our radial velocity and photometric monitoring results for six stars of early F type, which are pulsators of small amplitude. Methods. To determine the radial velocity of low signal-to-noise ratio time-series data, we constructed dedicated autocorrelation masks based on high signal-to-noise ratio spectra, used in our published chemical studies. The radial velocity variations were analysed in detail to differentiate between pulsational variability and variability caused by orbital motion. When available, the photometric monitoring data were used to complement the time series of radial velocity data and to establish the nature of the pulsation. Finally, orbital minimalisation was performed to constrain the orbital elements. Results. All of the six objects are binaries with orbital periods ranging from 120 to 1800 days. Five systems have non-circular orbits. The mass functions range from 0.004 to 0.57 M and the companions are probably unevolved objects of (very) low initial mass. We argue that these binaries must have evolved through a phase of strong binary interaction when the primary was a cool supergiant. Although the origin of the circumstellar disc is not well understood, the disc is generally believed to have formed during this strong interaction phase. The eccentric orbits of these highly evolved objects remain poorly understood. In one object, the line-of-sight grazes the edge of the puffed-up inner rim of the disc. Conclusions. These results corroborate our earlier statement that evolved objects in binary stars create a Keplerian dusty circumbinary disc. With the measured orbits and mass functions, we conclude that the circumbinary discs seem to have a major impact on the evolution of a significant fraction of binary systems. Tables 4-6 are only available in electronic form at

We present the results of a spectroscopic multisite campaign for the β Cephei star 12 (DD) Lacertae. Our study is based on more than thousand high‐resolution high S/N spectra gathered with eight different telescopes in a time span of 11 months. In addition, we make use of numerous archival spectroscopic measurements. We confirm 10 independent frequencies recently discovered from photometry, as well as harmonics and combination frequencies. In particular, the slowly pulsating B‐stars (SPB)‐like g‐mode with frequency 0.3428 d−1 reported before is detected in our spectroscopy. We identify the four main modes as (ℓ1, m1) = (1, 1), (ℓ2, m2) = (0, 0), (ℓ3, m3) = (1, 0) and (ℓ4, m4) = (2, 1) for f1= 5.178 964 d−1, f2= 5.334 224 d−1, f3= 5.066 316 d−1 and f4= 5.490 133 d−1, respectively. Our seismic modelling shows that f2 is likely the radial first overtone and that the core overshooting parameter αov is lower than 0.4 local pressure scale heights.

Aims. We present the results of a detailed analysis of 452 ground-based high-resolution high S/N spectroscopic measurements spread over 4.5 years for β Canis Majoris with the aim to determine the pulsational characteristics of this star, and to use them to derive seismic constraints on the stellar parameters. Methods. We determine pulsation frequencies in the Si III 4553 Å line with Fourier methods. We identify the m-value of the modes by taking into account the photometric identifications of the degrees ℓ. To this end we use the moment method together with the amplitude and phase variations across the line profile. The frequencies of the identified modes are used for a seismic interpretation of the structure of the star. Results. We confirm the presence of the three pulsation frequencies already detected in previous photometric datasets: f 1 = 3.9793 c d −1 (46.057 µHz), f 2 = 3.9995 c d −1 (46.291 µHz) and f 3 = 4.1832 c d −1 (48.417 µHz). For the two modes with the highest amplitudes we unambiguously identify (ℓ 1 , m 1 ) = (2, 2) and (ℓ 2 , m 2 ) = (0, 0). We cannot conclude anything for the third mode identification, except that m 3 > 0. We also deduce an equatorial rotational velocity of 31 ± 5 km s −1 for the star. We show that the mode f 1 must be close to an avoided crossing. Constraints on the mass (13.5 ± 0.5M ⊙ ), age (12.4 ± 0.7 Myr) and core overshoot (0.20 ± 0.05 H P ) of β CMa are obtained from seismic modelling using f 1 and f 2 .

Analyses of very accurate CoRoT space photometry, past Johnson V photoelectric photometry and high-resolution echelle spectra led to the determination of improved and consistent fundamental stellar properties of both components of AU Monocerotis. We derived new, accurate ephemerides for both the orbital motion (with a period of 11. d 113) and the long-term, overall brightness variation (with a period of 416. d 9) of this strongly interacting Be + G semi-detached binary. It is shown that this long-term variation must be due to attenuation of the total light by some variable circumbinary material. We derived the binary mass ratio M G /M B = 0.17 ± 0.03 based on the assumption that the G-type secondary fills its Roche lobe and rotates synchronously. Using this value of the mass ratio as well as the radial velocities of the G-star, we obtained a consistent light curve model and improved estimates of the stellar masses, radii, luminosities and effective temperatures. We demonstrate that the observed lines of the B-type primary may not be of photospheric origin. We also discover rapid and periodic light changes visible in the high-quality residual CoRoT light curves. AU Mon is put into perspective by a comparison with known binaries exhibiting long-term cyclic light changes.Based on photometry collected by the CoRoT space mission as well as spectroscopy obtained with the FEROS spectrograph attached to the 2.2-m telescope at European Southern Observatory (ESO), La Silla, Chile, under the ESO Large Programme LP178.D-0361, and with the SOPHIE spectrograph of the Observatoire de Haute-Provence (France). The CoRoT space mission was developed and is operated by the French space agency CNES, with the participation of ESA's RSSD