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Numerical simulations of the interstellar medium under the action of a density wave provide an accurate method for determining the positions of the main resonances in grand-design spiral galaxies. Barred spiral galaxies are among the best candidates for a single and well defined wave mode, because bars are standing waves which may share the same

We have observed HD 101177B and 149414A, two known single-lined binaries, and directly measured the radial velocities of their secondaries, enabling us to derive the mass ratios of the two systems. Using high signal-to-noise ratio spectra obtained mostly with the William Herschel Telescope, and a new algorithm to analyse composite spectra, TODCOR

We obtained long-slit spectroscopy of the Sb NGC 7331 and the barred NGC 5728 galaxies at the 4.2 m William Herschel Telescope with the ISIS spectrograph. We have determined the stellar Line of Sight Velocity Distribution (LOSVD), using the near-IR CaII triplet ( ~ 8500 Angstroms), along the major axis of these two galaxies. The analysis of NGC

We have obtained deep CCD R and I mosaic imaging of 578 arcmin^2^ within 1°.5 of the Pleiades' center - reaching a completeness magnitude I = 19.5 - with the aim of finding free-floating brown dwarfs. Teide 1, the best bona fide brown dwarf discovered so far in the cluster (Rebolo, Zapatero Osorio & Martin, 1995Natur.377..129R), arose as a result

We present a model for the evolution of the light-nuclide abundances in the Galaxy, aimed especially at interpreting the observed beryllium and boron abundances as a function of that of iron. We present two models, one for the Galactic halo and the other for the Galactic disk. The main characteristics of the halo model are (1) the relatively rapid