Adaptive optics devices in astronomy compensate the distortions introduced by the atmosphere in the quality and resolution of images taken by ground-based telescopes. The proper knowledge of the spatial and temporal behaviour of the atmospheric turbulence is crutial for optimizing the design of multiconjugate adaptive optics systems to satisfy the

The Gran Telescopio Canarias (GTC) is a 10m segmented mirror telescope that is under construction at the Observatorio del Roque de los Muchachos (Spain) and that is expected to have first light during 2006. The telescope mechanics is comprised of the telescope structure, bearings, motors, encoders, brakes, cable wraps and counterweights and also

We present Na, Mg and Al abundances in a set of 98 stars with known giant planets, and in a comparison sample of 41 "single" stars. The results show that the [X/H] abundances (with X = Na, Mg and Al) are, on average, higher in stars with giant planets, a result similar to the one found for iron. However, we did not find any strong difference in the

We present medium-resolution optical spectra of the secondary star in the high Galactic latitude black hole X-ray binary XTE J1118+480 and determine the abundance of Mg, Al, Ca, Fe, and Ni in its atmosphere. For all the elements investigated, we find supersolar abundances; thus, we reject the hypothesis that the black hole came from the direct

Microquasars are binary star systems with relativistic radio-emitting jets. They are potential sources of cosmic rays and can be used to elucidate the physics of relativistic jets. We report the detection of variable gamma-ray emission above 100 gigaelectron volts from the microquasar LS I +61 303. Six orbital cycles were recorded. Several

We have expressed in linearized form the five classical coupled equations representing the rotating gas disk of a standard disk galaxy. We solve them in three limiting cases for the gas disk: (1) infinite thickness and uniform rotation, (2) finite thickness and uniform rotation, and (3) infinite thickness and a shearing box approximating