We present well-sampled uvby light curves, supplemented by a few β filter measurements, of the Algol binary VV UMa. The light curves are analysed using two different codes to derive the orbital and absolute stellar parameters of this binary. We find reasonably good fits to the light curves and determine the stellar effective temperatures Teff,1~

The equilibrium configuration of very small magnetic flux tubes in an intergranular environment automatically produces kilogauss magnetic field strengths. We argue that such a process takes place in the Sun and complements the convective collapse (CC), which is traditionally invoked to explain the formation of kilogauss magnetic concentrations in

We combine results from imaging searches for substellar objects in the σ Orionis cluster and follow-up photometric and spectroscopic observations to derive a census of the brown dwarf population in a region of 847 arcmin2. We identify 64 very low mass cluster member candidates in this region. We have available three-color (I, Z, and J) photometry

We present our recent spectrophotometric results of the infrared luminous Seyfert 2 galaxy NGC 7679. We find compelling evidence for the presence of a recent nuclear starburst, revealed by the observations of a) the spectral features of high order Balmer absorption lines, b) the weak equivalent widths for CaIIK lambda 3933, CN lambda 4200, G-band

We report new (1995) Very Large Array (VLA) observations and (1984-1999) Effelsberg 100 m monitoring observations of the 22 GHz H2O maser spectrum of the Seyfert 2 galaxy NGC 1068. The sensitive VLA observations provide a registration of the 22 GHz continuum emission and the location of the maser spots with an accuracy of ~5 mas. Within the

The term "Target of Opportunity" (ToO) is used in astronomy to identify unpredictable events whose study is of the highest scientific interest. For XMM-Newton a ToO is an astronomical event observable by its instruments, which cannot be predicted and scheduled on the time scale of one year, yet is scientifically significant enough to justify the