The two main perturbative schemes for the non-linear evolution of large-scale structures are the Lagrangian and the Eulerian ones. The former has been set as a much more powerful technique, due to its property of yielding the exact solution in the plane-symmetric case. We have applied the Eulerian scheme to this plane symmetric case and have

We present the results of optical photometry of the X-ray transient XTE J2123-058. CCD R-band images, have been obtained since 2 Jul until 29 Sep 1998. Following the behaviour of the XTE/ASM lightcurve, the system decline optically from the begining of August at approximately 0.1 mag/day. Despite the drop in luminosity, we observe a dramatic

A sample of 47 faint Gigahertz Peaked Spectrum (GPS) radio sources selected from the Westerbork Northern Sky Survey (WENSS) has been imaged in the optical and near-infrared, resulting in an identification fraction of 87 per cent. The R-IR-K colours of the faint optical counterparts are as expected for passively evolving elliptical galaxies

We have studied analytically the mean pull on shells of real (anisotropic and/or non-isolated) mass concentrations. Using a non-linear scheme, the radial component of the peculiar velocity is averaged over solid angle (V_0) and mass-averaged (V^*_0) for several different generic configurations. Nine Local Supercluster(LS)-like objects and six Great

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Nitrogen lines of the N I lambda1134 and lambda1200 multiplets in the damped Lyalpha (DLA) galaxies at z_abs = 2.309, 2.827, and 3.025 toward the QSOs 0100+1300, 1425+6039, and 0347-3819, respectively, have been detected by means of high-resolution spectra (R ~ 2 x 10^4) obtained with 4 m class telescopes at ESO (La Silla, Chile) and the