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Context. Rapid advancements in light-curve and radial-velocity curve modelling, as well as improvements in the accuracy of observations, allow more stringent tests of the theory of stellar evolution. Binaries with rapid apsidal advance are particularly useful in this respect since the internal structure of the stars can also be tested. Aims. Thanks to its long and rich observational history and rapid apsidal motion, the massive eclipsing binary Y Cyg represents one of the cornerstones of critical tests of stellar evolutionary theory for massive stars. Nevertheless, the determination of the basic physical properties is less accurate than it could be given the existing number of spectral and photometric observations. Our goal is to analyse all these data simultaneously with the new dedicated series of our own spectral and photometric observations from observatories widely separated in longitude. Methods. We obtained new series of UBV observations at three observatories separated in local time to obtain complete light curves of Y Cyg for its orbital period close to 3 days. This new photometry was reduced and carefully transformed to the standard UBV system using the HEC22 program. We also obtained new series of red spectra secured at two observatories and re-analysed earlier obtained blue electronic spectra. Reduction of the new spectra was carried out in the IRAF and SPEFO programs. Orbital elements were derived independently with the FOTEL and PHOEBE programs and via disentangling with the program KOREL. The final combined solution was obtained with the program PHOEBE. Results. Our analyses provide the most accurate value of the apsidal period of (47.805 ± 0.030) yr published so far and the following physical elements: M 1 = 17.72 ± 0.35 M , M 2 = 17.73 ± 0.30 M , R 1 = 5.785 ± 0.091 R , and R 2 = 5.816 ± 0.063 R . The disentangling thus resulted in the masses, which are somewhat higher than all previous determinations and virtually the same for both stars, while the light curve implies a slighly higher radius and luminosity for star 2. The above empirical values imply the logarithm of the internal structure constant log k 2 = −1.937. A comparison with Claret's stellar interior models implies an age close to 2 × 10 6 yr for both stars. Conclusions. The claimed accuracy of modern element determination of 1-2 per cent still seems a bit too optimistic and obtaining new high-dispersion and high-resolution spectra is desirable.

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Abstract. We present a Doppler Image of the oxygen abundance distribution over the surface of the star θ Aur. The symmetry of the oxygen distribution appears to be consistent with the magnetic field observations such that the oxygen is highly depleted at the magnetic poles. In contrast to the star UMa, where the oxygen displayed undepleted solar abundance in a band around the magnetic equator, for θ Aur the instances of more normal solar levels of abundance occur in bands midway between the magnetic poles and the magnetic equator. The oxygen abundance at the magnetic equator is only mildly depleted for θ Aur. It is suggested that the oxygen abundance distribution is consistent with a global field that has a strong quadrupolar component. A detailed comparison is made between the oxygen abundance distribution and that of the distribution of chromium as mapped by Hatzes (1991a). A striking asymmetry is apparent in the contrasting behaviour of the oxygen and chromium abundance pattern at the two magnetic poles.

Doppler frequently shifts for a laser field interacting with a diverging supersonic atomic beam are canceled using spatially varying Zeeman shifts. Dense atomic beams with long interaction path lengths and narrow linewidths are obtained for spectroscopic and nonlinear-optics applications.

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Abstract. New light and radial-velocity curves of V497 Cep, a binary in the open cluster NGC 7160, were obtained and the linear ephemeris of the system was refined to HJD (Min I) = (2 446 299.1596 ± 0.0064)The first light and radial-velocity curve solutions allowed us to derive the basic physical properties of this astrophysically important binary. It was found that the observed light variation of V497 Cep consists of a strong ellipticity effect and a small contribution from grazing eclipses. A comparison of masses and radii of V497 Cep with theoretical evolutionary tracks indicates that both binary components are very close to the zero-age main sequence. A comparison of disentangled line profiles of the He I 6678 line with synthetic, rotationally broadened line profiles indicates that the rotation of both stars is synchronized with the orbital revolution as expected. This finding increases the credibility of our solutions. We find E(B − V) = 0. m 39. The distance to the cluster NGC 7160 was found to be about 760 (±100) pc which agrees well with other available estimates.