We present the optical and UV emission-line properties of 160 X-ray-selected active galactic nuclei (AGN) taken from the RIXOS survey (including Hα, Hβ, [Oiii] lambda5007, Mgii lambda2798 and Ciii] lambda1909). This sample is believed to contain a mixture of absorbed and unabsorbed objects, with column densities up to ~4x10^21cm^-2. Although the

Nine months' seeing statistics at the Observatorio del Roque de los Muchachos (ORM) are presented. Measurements were taken with a differential image motion monitor on top of a 5-m high tower. From the whole campaign the mean seeing is 0.76", the median value is 0.64" and 7% of the time the seeing is better than 0.3". The best seeing measured is 0

The in-flight performance of the total and spectral irradiance instruments within VIRGO (Variability of solar IRradiance and Gravity Oscillations) on the ESA/NASA Mission SOHO (SOlar and Heliospheric Observatory) is in most aspects better than expected. The behaviour during the first year of operation of the two types of radiometers and the

The properties of the photosphere in magnetic and non magnetic regions, at two levels in the solar atmosphere, have been studied, using two virtually simultaneous time sequences of 109 mn duration of CCD images taken at the Vacuum Tower Telescope of the Sacramento Peak Observatory. The selected wavelengths correspond to the true continuum and to

This article presents a statistical-mechanical treatment of a relationship (the force equation) between the gravitational potential for two particles and the correlation functions in a relaxed distribution of particles with different masses. This relationship is used in the case of galaxies interacting through a Newtonian potential in a Universe in

After 8 months of nearly continuous measurements the GOLF instrument, aboard SOHO, has detected acoustic mode frequencies of more than 100 modes, extending from 1.4 mHz to 4.9 mHz. In this paper, we compare these results with the best available predictions coming from solar models. To verify the quality of the data, we examine the asymptotic