Infrared magnitudes in the J, H, K and L bands for 64 metal-deficient stars spanning a wide range in effective temperature, luminosity and metal content are presented. An accuracy of 0.02 magnitude is obtained for the JHK bands and 0.03 for the L filter. Infrared-infrared and optical-infrared colour-colour diagrams are discussed and compared with

EL TRABAJO ES UN ANALISIS ESPECTROPOLARIMETRICO DE LAS CONCENTRACIONES MAGNETICAS IRRESUELTAS ESPACIALMENTE EN FACULAS SOLARES. EN EL MISMO SE ESTUDIANOBSERVACIONES EN ALTA COMO EN BAJA RESOLUCION ESPACIAL (1 Y 10 RESPECTIVAMENTE). SE PROPONE UN NUEVO METODO DE DETERMINACION DE PARAMETROS DE DICHAS ESTRUCTURAS (TAMBIEN CONOCIDAS COMO TUBOS DE FLUJO

LAS OBSERVACIONES ESPECTROSCOPICAS REALIZADAS EN MAS DE SESENTA ESTRELLAS CARACTERIZADAS POR SU DEFICIENCIA METALICA RESPECTO AL SOL O POR SU PERTENENCIAA CUMULOS ABIERTOS ESTELARES CON EDADES BIEN DEFINIDAS DESPUES DE SER ANALIZADAS EMPLEANDO MODELOS DE ATMOSFERAS Y LA TECNICA DE SINTESIS ESPECTRAL HAN PERMITIDO INVESTIGAR DIVERSOS PUNTOS DE

An analysis has been carried out of the center-to-limb variation of the apparent sizes of the umbra, penumbra, and whole spot. It has revealed that the umbral size decreases with height. This result is interpreted in terms of the penumbral geometrical height scale. A value of 230 km, which is larger than that of the photosphere or the umbra

BVJK light curves of CG Cygni show an apparent infrared excess 0.2 mag out of eclipse, assuming the spectral types of the components to be G9.5V + K3V. The depths of the eclipses also show an excess equal (within the errors) to that at quadrature. The source of these excesses is most probably a circum-system shell of cool material; it cannot be

As the triangular libration points in the Earth-Moon system are of potential interest for optical interferometry, their dynamical property was analyzed adopting realistic models. Quasi-periodic orbits were identified, and their stability investigated. Results show that relative motion leads to baseline variation of 1 to 20 cm/sec, which may be