We report on the discovery of 15 new weak-line T Tauri stars (wTTS) south of the Taurus molecular clouds based on the large database produced by the ROSAT All-Sky Survey. High-resolution spectroscopy of 109 optical counterparts of X-ray sources has been performed to measure their radial velocities in order to verify kinematic membership to the

The models for galaxy clustering in which galaxies are identified with peaks on the mass density field smoothed on an appropriate scale are plagued by some difficulties. We discuss them here, propose an alternative model that avoids them and compute the correlation functions implied by it. This model has been developed within the context of the

PG 0122+200 is a hot pulsating PG 1159 [GW Virginis] star. This paper describes the results of two, bi-site, time-series photometric observational campaigns. The observed complex light curve is interpreted as resulting from a mixture of non radial g-mode pulsations. There appear to be at least ten independent frequencies in the power spectrum. The

IAUC 6193 available at Central Bureau for Astronomical Telegrams. IAUC 6193 available at Central Bureau for Astronomical Telegrams.

Time series of white-light pictures of the sunspot NOAA 7522, obtained at the Swedish Vacuum Solar Telescope (La Palma), were analyzed to study the proper motion of bright features in sunspots. For the first time, its relation with the dark nuclei present in the umbra is investigated. The bright features are visible in the penumbra as bright grains

LA TESIS PRESENTA UN ESTUDIO OBSERVACIONAL DE LOS PROCESOS DE FORMACION ESTELAR A GRAN ESCALA Y SU RELACION CON LAS ONDAS DE DENSIDAD PRESENTES EN LAS GALAXIAS BIEN DISEÑADAS DE TIPO INTERMEDIO. SE HA DEMOSTRADO, CON UN ALTO GRADO DE FIABILIDAD, QUE LA INTENSIDAD DE LA ONDA Y LA INTENSIDAD DE FORMACION ESTELAR MEDIDAS A LO LARGO DE LOS BRAZOS NO