Esta tesis se centra en el estudio de las estrellas subenanas calientes de tipo B (sdBs). Esta clase de objetos muestran propiedades espectrales similares a las estrellas de tipo B en la Secuencia Principal, y se caracterizan por una baja luminosidad, que las sitúa por debajo de dicha secuencia en un diagrama de Hertzsprung-Russell. Actualmente las

We present a detailed stellar population analysis of 27 massive elliptical galaxies within four very rich clusters at redshift z ~ 0.2: A115, A655, A963 and A2111. Using the new, high-resolution stellar populations models developed in our group, we obtained accurate estimates of the mean luminosity-weighted ages and relative abundances of CN, Mg

Time-resolved medium resolution spectroscopy is presented for six cataclysmic variables discovered by the Sloan Digital Sky Survey. For four of these systems the data are extensive enough to determine orbital periods from measurements of the radial velocity motion of the Balmer emission lines. For one of the systems we also present time-resolved

Time-resolved medium resolution spectroscopy is presented for six cataclysmic variables discovered by the Sloan Digital Sky Survey. For four of these systems the data are extensive enough to determine orbital periods from measurements of the radial velocity motion of the Balmer emission lines. For one of the systems we also present time-resolved

Extinction due to intergalactic grey dust has been proposed as an alternative to accelerated expansion to account for the dimming of SnIa fluxes beyond z ≃ 0.5. The "replenishing" grey dust model, although fitting the observational data, does not seem to be based on physical assumptions. For this reason, in this paper we propose a new grey dust

Measuring the population of obscured quasars is one of the key issues in understanding the evolution of active galactic nuclei (AGNs). With a redshift completeness of 99%, the X-ray sources detected in the Chandra Deep Field South (CDF-S) provide the best sample for this issue. In this paper, we study the population of obscured quasars in CDF-S by