Stellar-mass black holes have all been discovered through X-ray emission, which arises from the accretion of gas from their binary companions (this gas is either stripped from low-mass stars or supplied as winds from massive ones). Binary evolution models also predict the existence of black holes accreting from the equatorial envelope of rapidly

La búsqueda de planetas extrasolares se ha convertido en uno de los campos de mayor interés de la Astrofísica en los últimos años. Desde el descubrimiento del primer planeta fuera del Sistema Solar orbitando una estrella de secuencia principal en 1995, el número de planetas detectados ha crecido exponencialmente. Aunque la mayoría de los

We present an overview of and status report on XSL, the X-Shooter Spectral Library. XSL is an ESO Large Programme that is using the X-Shooter three-beam spectrograph to collect moderate-resolution (R=7000--11000), high signal-to-noise spectra of more than 700 stars across the Hertzsprung-Russell diagram with a large range of compositions. XSL is

In 1995, after many years of intense observational efforts, brown dwarfs were finally discovered in a star cluster and also orbiting a star. The work that led to the discovery and characterization of the brown dwarf Teide 1 is described here. This very red object was detected in optical images of the central region of the Pleiades cluster obtained

Various aspects of the magnetism of the quiet sun are reviewed. The suggestion that a small scale dynamo acting at granular scales generates what we call the quiet sun fields is studied in some detail. Although dynamo action has been proved numerically, it is argued that current simulations are still far from achieving the complexity that might be

We present a detailed and uniform study of oxygen abundances in a large sample of solar-type stars. EW measurements were carried out for the [OI] 6300 Å and the OI 6158 Å lines and LTE abundance results for these indicators were obtained in 611 and 535 stars respectively. 411 stars have oxygen derived from both indicators, which allows us to