Over the last 20 years, the surface abundance of Li has been derived for a significant number of low mass pre-main sequence (PMS) stars. Several works have pointed out the unexpected large Li spread for young stars of similar ages and masses. This spread still represents a challenge in our understanding of PMS stellar evolution. Almost in parallel

STARS is an asteroseismology mission, which, through the acquisition of very accurate light curves, will detect oscillations in a wide variety of stars. This will allow, for the first time, the internal structure of stars of different age, composition and spectral type, to be studied directly, bringing the spectacular successes of helioseismology

We tackle here the problem of obtaining the spatial density of sources ρ in the bulge of a spiral galaxy using bidimensional surface photometry. V,R,I,Z CCD images, taken with the 4.2m William Herschel Telescope at seeing limit resolution (0.5"-1.1"), yield the photometric parameters for the galaxy NGC 2841. The necessary procedure prior to

By adopting the thin flux tube model as representative of spatially unresolved magnetic elements in the photosphere of the Sun, we identify an adequate set of parameters for the model and derive the corresponding response functions (RFs) which inform about the variation of the emergent Stokes spectrum when such parameters are perturbed. We

The study of the storage of toroidal flux tubes at the base of the convection zone is of interest in connection with the operation of a solar αΩ-type dynamo. The natural equilibrium state for an isolated flux tube is that of neutral buoyancy (so that there is a mass flow along the tube in the direction of solar rotation); flux tubes in thermal

A numerical code has been developed for modelling the asymmetries in three spectral lines (K I 7699, Fe I 5576 and Fe I 5635A) formed at different photospheric heights and observed in plage regions near the solar disk center. The aim of this work was to reproduce the absolute line bisectors obtained from low resolution observations. The mere