We have carried out an optical follow-up of twelve ROSAT discovered candidate members of the Coma Berenices open cluster. VRI photometry and low resolution ( ~ 3 Å) spectroscopy in the range 3800-7000 Åwere performed to obtain colour-magnitude diagrams, proper motions, spectral types, chromospheric activity levels and radial velocities that allow

We present contemporaneous optical and infrared (IR) photometric observations of the Type IIn SN 1998S covering the period between 11 and 146d after discovery. The IR data constitute the first ever IR light curves of a Type IIn supernova. We use blackbody and spline fits to the photometry to examine the luminosity evolution. During the first 2-3

We present the near infrared photometry of a new sample of 225 IRAS sources, many of them previously unidentified in the literature, selected because their far infrared colours are similar to those shown by known planetary nebulae. The results obtained are used to establish the main source of near infrared emission. Combining this information with

We present near-infrared photometry and optical spectroscopy of very low mass stars and brown dwarf candidates in the Pleiades open cluster. The membership status of these objects is assessed using color-magnitude diagrams, lithium and spectral types. Eight objects out of 45 appear to be nonmembers. A search for companions among 34 very low mass

We present a preliminary analysis of ISO-SWS spectra of a sample of Vega-type and pre-main sequence stars, which were observed from the ground in a project devoted to the study of formation and evolution of planetary systems, carried out during the 1998 International Time of the Canary Islands Observatories. ISO-SWS covers many interesting features

En este trabajo de Tesis Doctoral se analizan y modelizan los diferentes aspectos que tienen influencia en la calidad de imagen de telescopios con espejo primario segmentado. Este trabajo, que se enmarca en el entorno del diseño y construcción del Gran Telescopio de Canarias (GTC), particulariza su desarrollo para el esquema de segmentación del GTC