We present the results of a detailed analysis of 121 ground-based high-resolution, high signal-to-noise ratio spectroscopic measurements spread over 3 yr for the β Cephei star θ Ophiuchi. We discovered θ Oph to be a triple system. In addition to the already known speckle B5 companion of the B2 primary, we showed the presence of a low-mass

We define and study a family of cubic surfaces in the projectivized tangent bundle over a four dimensional projective space associated to the root system D_5. The 27 lines are rational over the base and we determine the classifying map to the moduli space of marked cubic surfaces. This map has degree two and we use it to get short proofs for some

We perform a chi ^{2} fit at 95% CL to obtain model-dependent bounds to Z-Z' mixing angle theta and Z_2-mass in the framework of SU(3)_C X SU(3)_L X U(1)_X models with beta arbitrary. Using experimental results at the Z-pole and atomic parity violation, we obtain allowed regions according to the value of beta and depending on the assignment of the

New polarization data at 850 microns of OMC2 in Orion A are presented. These measurements trace the direction of magnetic fields in the densest parts of the filamentary molecular clouds and form a part of the comparison of magnetic-field directions at various spatial and density scales. They allow us to put constraints on existing models, and

SW Sextantis stars are a relatively large group of cataclysmic variables whose properties contradict all predictions made by the current CV evolution theories. Very little is known about the properties of their accreting white dwarfs and their donor stars, as the stellar components are usually outshone by an extremely bright accretion flow

We present time-resolved optical spectroscopy and photometry of three new relatively bright (V˜14.0-15.5) long-period cataclysmic variables discovered in the Hamburg Quasar Survey: HS 0139+0559, HS 0229+8016 and HS 0506+7725. The orbital periods, 243.2±0.4 min, 233±1 min and 212.6±0.1 min, are determined from radial velocity studies. The light