Esta tesis esta dedicada al estudio de las anisotropías de la Radiación Cósmica de Microondas (RCM) en escalas angulares intermedias (entre 2º y 30'), usando para ello dos experimentos interferométricos: el interferómetro "JB-IAC", y el "Very Small Array" (VSA). Ambos instrumentos operan a una frecuencia próxima a los 30 GHz. Con el JB-IAC, se han

We present high time resolution spectroscopy of the non-eclipsing old nova V533 Herculis (N Her 1963). It is the second nova remnant affected by the `SW Sex syndrome'. A modulation of the equivalent width of the emission lines with a period of 23.33 min has been detected. This, together with the strong He II λ4686 emission characteristic of

We describe the construction and study of an objectively defined sample of early-type galaxies in low-density environments. The sample galaxies are selected from a recently completed redshift survey using uniform and readily quantified isolation criteria, and are drawn from a sky area of ~700 deg2, to a depth of 7000 km s-1 and an apparent

In this brief note we remark that the four spatially resolved relativistic radio jets among the 14 dynamically confirmed black hole x-ray novae are all in systems with long orbital periods. Many shorter period systems show transient radio outbursts which are attributed to jets, but these jets have not been resolved. Super-Eddington accretion has

We present observations of eight Galactic bulge microlensing events taken with the 1.0-m Jacobus Kapteyn Telescope (JKT) on La Palma during 2000 June and July. The JKT observing schedule was optimized using a prioritizing algorithm to automatically update the target list. For most of these events we have sampled the light curves at times where no

Absolute and differential chemical abundances are presented for the largest group of massive stars in M 31 studied to date. These results were derived from intermediate resolution spectra of seven B-type supergiants, lying within four OB associations covering a galactocentric distance of 5-12 kpc. The results are mainly based on an LTE analysis