We present optical and infrared observations of Roque Praesepe 1 (RPr 1), a faint ( I=21.01 ) and very red object ( I-K=4.57 ) discovered in a deep CCD survey, covering an area of 800 arcmin2 of the Praesepe open cluster. A low-resolution spectrum shows that RPr 1 is a very late object, the latest object in Praesepe for which a spectrum has been

The blazar 3C 279, one of the brightest identified extragalactic objects in the gamma -ray sky, underwent a large (factor of ~10 in amplitude) flare in gamma -rays toward the end of a 3 week pointing by Compton Gamma Ray Observatory (CGRO), in 1996 January-February. The flare peak represents the highest gamma -ray intensity ever recorded for this

There are two principal problems in explaining, in terms of the emission from OB stars, the ionisation of the gas which emits the diffuse H-alpha in spiral galaxies. One is the long pathlengths which the ionising photons need to traverse to reach their objectives, the other is whether sufficient photons can escape from within the HII regions which

Since its discovery in 1992, the superluminal X-ray transient GRS 1915+105 has been extensively observed in an attempt to understand its behavior. We present here first results from a multiwavelength campaign undertaken from 1996 July to September. This study includes X-ray data from the RXTE All Sky Monitor and BATSE, two-frequency data from the

En la memoria de Tesis se recoge un archivo de espectros de supernovas. Para cada supernova estudiada se ha procurado obtener una secuencia de espectros que abarque la mayor parte de su historia evolutiva. Este trabajo es el resultado de un esfuerzo de muchos años durante los que se han ido observando un gran número de objetos. Además de su

The complete set of data from the Tenerife 10-GHz (8-deg FWHM) twin-horn, drift scan experiment is described. These data are affected by both long-term atmospheric baseline drifts and short-term noise. A new maximum entropy procedure, utilizing the time invariance and spatial continuity of the astronomical signal, is used to achieve a clean