We present results on the star formation history of the Local Group dSph galaxy Leo I, obtained through the analysis of its deep HST color-magnitude diagram (CMD) using model CMDs computed from stellar evolutionary models. Our results show unambiguously that Leo I experienced a major increase of its star formation rate from about 6 Gyr ago to 2 Gyr

We present the results of a cosmic microwave background (CMB) anisotropy ground-based millimetric experiment sensitive to fluctuations on angular scales of ~2 deg. Four independent bands centered at 3.3, 2.1, 1.3, and 1.1 mm collected ~550 hr of observation during the summer of 1994. The instrument was located on the island of Tenerife at an

We have completely mapped the Galactic globular cluster NGC 1851 with large-field, ground-based VI CCD photometry and pre-repair HST/WFPC1 data for the central region. The photometric data set has allowed a V vs. (V-I) colour-magnitude diagram for ~ 20500 stars to be constructed. >From the apparent luminosity of the horizontal branch (HB) we derive

En esta Tesis Doctoral, tras una introducción sobre las estructuras magnéticas solares, en particular aquéllas no resueltas espacialmente, sus observaciones y técnicas de diagnóstico, y el problema del transporte de radiación polarizada en presencia de campo magnético, se presenta un nuevo código de inversión de la ecuación de transporte radiativo

IAUC 6902 available at Central Bureau for Astronomical Telegrams.

We report on the results of optical follow-up observations of the counterpart of GRB970508 between 7 hours and 100 days after the event. Multi-colour U, B, V, Rc and Ic band observations were obtained during the first three consecutive nights. The Rc light curve rises to a maximum 1.8 days after the burst and after this declines with a power law