This article presents an introduction to optical pumping, atomic polarization and the Hanle effect in weakly magnetized stellar atmospheres. Although the physical processes and the theoretical framework described here are of interest for applications in a variety of astrophysical contexts (e.g. scattering polarization in circumstellar envelopes and

Not Available

Four years of GOLF velocity time series have been used to study the low frequency part of the solar spectrum below 1.5 mHz. This paper discusses the methods already developed for the research of the low-degree low-order acoustic modes by Garcia et al. (2000) and for the gravity modes by Turck-Chieze et al. (2000). These methods are based on our

Nuestro objetivo es mejorar los analisis espectroscopicos para intentar obtener la descripcion mas realista posible de las atmosferas de las estrellas OB de la Galaxia. De esta manera podremos responder a ciertas preguntas que esten abiertas hoy en dia sobre estos objetos, en especial a si la discrepancia de He se puede explicar via procesos de

From an analysis of the stars remaining in central regions of the Galaxy after subtracting those belonging to the disc and the bulge, we deduce that the inner bulge must have an extra young population with respect to the rest of the bulge. It is shown that there is a higher ratio of very bright stars in the central bulge than there is in the outer

A most desirable feature of a standard candle to estimate astronomical distances is robustness against changes in metallicity and age. It is argued that the radii of main-sequence stars with spectral types from solar to A0 show predictable changes with metallicity and detectable changes with evolution. Such stars populate the solar neighborhood and