As part of a long term effort to understand pre-main sequence Li burning, we have obtained high resolution spectroscopic observations of 14 late type stars (G0-M1) in the young open cluster IC 4665. Most of the stars have Hα filled-in and LiI absorption, as expected for their young age. From the equivalent widths of Hα emission excess (obtained

We present high-resolution images of three BL Lac objects (0814+425, 1823+568, 2254+074) taken with the WFPC-2 camera on Hubble Space Telescope (HST) as part of a study of BL Lacs from a complete radio-selected sample. In two cases we clearly detect the host galaxies while the third BL Lac (0814+425) is unresolved. The host galaxy of 2254+074 is a

We monitored the light variations of 58 weak-line T Tauri stars in Taurus, recently discovered in the X-ray wavelength range during the ROSAT All-Sky Survey. We derive photometric periods for 18 stars, all but one being ascribed to rotational modulation by stellar spots. The exception is a 37.6d period assigned to the orbital motion of a new pre

EL TRABAJO RECOGIDO EN LA PRESENTE MEMORIA DESCRIBE UN EXPERIMENTO ENCAMINADO HACIA LA DETECCION DE MODOS GRAVITATORIOS SOLARES. LOS DATOS TOMADOS EN EL OBSERVATORIO DEL TEIDE ENTRE LOS AÑOS 1991 Y 1993, CONSISTEN EN MEDIDAS DIARIAS DE VELOCIDAD SOLAR OBTENIDAS SECUENCIALMENTE EN SEIS POSICIONES DIFERENTES Y SIMETRICAS SOBRE EL DISCO SOLAR. EL

Knowledge of the solar irradiance background is of great importance to solar and stellar physics. In particular, its contribution to the solar oscillations power spectrum is highly relevant as it represents the ultimate limit to the sensitivity of solar oscillations' observations. An analysis of the power spectra of the solar photometric data

A low dispersion objective-prism survey for low-redshift emission-line galaxies (ELGs) is being carried out by the University Complutense de Madrid with the Schmidt telescope at the German-Spanish Observatory of Calar Alto (Almeria, Spain). A 4° full aperture prism, which provides a dispersion of 1950Å/mm, and IIIa-F emulsion combination has been