High resolution, high signal to noise spectral profiles of the 8498 and 8542 A lines of the Ca II infrared triplet (IRT) have been obtained for a sample of late type dwarfs, with a wide range of levels of chromospheric activity, in the spectral range F9 to K4/5. These profiles, and the difference profiles for selected active and quiescent objects

As a result of a major program of spectral observations using the CAT 1.4 m telescope and Coude Echelle Spectrograph at ESO, La Silla, 68 high resolution profiles of the 3968.5 A Ca H resonance line have been obtained for 16 late type stars (dwarfs and subgiants, including the sun) ranging from F9 to K5, selected to be representative of a wide span

EN EL TRABAJO SE HA DETERMINADO LA ABUNDANCIA DE OXIGENO EN 43 ESTRELLAS ENANAS POBRES EN METALES PERTENECIENTES AL HALO Y DISCO GALACTICO A PARTIR DE ESPECTROS DE ALTA RESOLUCIO. LAS OBSERVACIONES SE REALIZARON EN EL TELESCOPIO ISAAC NEWTON DE 2.5 M, UTILIZANDO EL ESPECTROGRAFO DE DISPERSION INTERMEDIA Y DETECTORES CCD. SE HA ENCONTRADO QUE LA

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In its most general acceptation, surface photometry is a technique applicable to any "extended" object, irrespective of the spectral band of the observational frame. The subject of this paper is restricted to the mapping of galaxies in the "standard" bands of the visible. By combining CCD images with deep large-field photographs, this technique

The influence of rotation and finite size of the radiation source on the orbits of dust particles around stars is analyzed. It is found that there are physical situations in which the results first derived by Robertson (Poynting-Robertson effect), corresponding to a nonrotating point-like source, cannot properly describe the dynamical behavior of