ROSAT Position Sensitive Proportional Counter (PSPC) observations of the double-lobed radio source 3C 390.3 show resolved X-ray emission spatially located at the position of the northern radio hotspot. Possible origins for this X-ray emission are discussed. It is found that neither thermal emission nor inverse Compton emission could account for the

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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