The spectrum of the Be star o Pup is shown to vary periodically with a period of 28.9 days. A radial-velocity variable He i 6678 Å emission component suggests that the star is the same type as φ Per, 59 Cyg, and FY CMa, i.e. binaries consisting of a Be star and a hot companion that illuminates the Be star disk (also called φ Per-type binaries or Be+sdO binaries). The range of radial-velocity variations of the stronger emission component in the helium line observed in o Pup is about 270 km s −1 , a value in good agreement with the range derived for φ Per-type binaries. The radial velocity curves defined by the prominent emission peak in He i 6678 Å line and Hα + Paschen emission move in anti-phase. We suggest that o Pup is generically similar to φ Per-type systems and may represent the fourth case of a Be star with a hot subdwarf companion.

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Context. The study of apsidal motion in detached eclipsing binary systems is known to be an important source of information about stellar internal structure as well as the possibility of verifying of General Relativity outside the Solar System. Aims. As part of the long-term Ondřejov and Ostrava observational projects, we aim to measure precise times of minima for eccentric eclipsing binaries, needed for the accurate determination of apsidal motion, providing a suitable test of the effects of General Relativity. Methods. About seventy new times of minimum light recorded with photoelectric or CCD photometers were obtained for ten eccentric-orbit eclipsing binaries with significant relativistic apsidal motion. Their O-C diagrams were analysed using all reliable timings found in the literature, and new or improved elements of apsidal motion were obtained. Results. We confirm very long periods of apsidal motion for all systems. For BF Dra and V1094 Tau, we present the first apsidalmotion solution. The relativistic effects are dominant, representing up to 100% of the total observable apsidal-motion rate in several systems. The theoretical and observed values of the internal structure constant k 2 were compared for systems with lower relativistic contribution. Using the light-time effect solution, we predict a faint third component for V1094 Tau orbiting with a short period of about 8 years.

Radial-velocity variations of the Hα emission measured on the steep wings of the Hα line, prewhitened for the long-time changes, vary periodically with a period of 218. d 025 ±0. d 022, confirming the suspected binary nature of the bright Be star BU Tau, a member of the Pleiades cluster. The orbit seems to have a high eccentricity over 0.7, but we also briefly discuss the possibility that the true orbit is circular and that the eccentricity is spurious owing to the phase-dependent effects of the circumstellar matter. The projected angular separation of the spectroscopic orbit is large enough to allow the detection of the binary with large optical interferometers, provided the magnitude difference primary − secondary is not too large. Since our data cover the onset of a new shell phase up to development of a metallic shell spectrum, we also briefly discuss the recent long-term changes. We confirm the formation of a new envelope, coexisting with the previous one, at the onset of the new shell phase. We find that the full width at half maximum of the Hα profile has been decreasing with time for both envelopes. In this connection, we briefly discuss Hirata's hypothesis of precessing gaseous disk and possible alternative scenarios of the observed long-term changes.