Doppler velocity data are used to study solar cycle variation of the frequencies of solar acoustic oscillations from 1977 to 1988. The results show a clear shift in frequency of the cross-correlation peaks of -0.37 + or - 0.04 microHz peak to peak as the solar activity cycle progresses from maximum to minimum. This effect is dependent on the l

The observations of the low-mass x ray binary, Cyg X-2, taken with the International Ultraviolet Explorer (IUE) in a campaign conducted in June and October of 1988 are reported. A direct relationship between the strength of the UV continuum and line emission and the placement of the x ray spectrum in one of three branches of the so-called Z-shaped

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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