We report the first detection of Ca II H and K absorption in the high-velocity cloud complex C, the largest HVC. Absorption is detected in the spectra of the quasar PG 1351+640 and of the Seyfert galaxy Mark 290, at velocities of -163 and -137km/s (see fig.2). The implied Ca+ abundances are about 2x10^-8^, or about 0.01 times the total solar

The direct identification of structure in the cosmic microwave background (CMB) is a major objective of observational cosmology. We present a detailed discussion of observations of such structure detected on a 5 deg scale in the CMB using beam-switching radiometers at 10, 15 and 33 GHz sited in Tenerife. This long-term experiment has reached

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