En la tesis se presenta un método para la inversión de los perfiles de Stokes de lineas espectrales para lasque la aproximación de Equilibrio Termodinámico Local no es adecuada. Este método es aplicado a observaciones espectro-polarimétricas realizadas con vistas al estudio de la dinámica y el magnetismo de la cromosfera sobre laumbra de las

We discuss results on the oxygen abundance in a sample of 23 metal-poor (-3.0≤ [Fe/H] ≤ -0.3) unevolved stars and one giant. High resolutionspectroscopy of OH lines in the near UV allowed us to trace the early evolution of oxygenversus metallicity. Contrary to previous expectations, we find that oxygen abundances derived from these low excitation

IAUC 7219 available at Central Bureau for Astronomical Telegrams.

We report optical observations of the GRB 980329 error box which represent the second earliest detection of the GRB 980329 optical transient. We determine R = 23.7 +/- 0.5 mag on 29.89 March, which is consistent with R = 23.6 +/- 0.2 mag as reported by Palazzi et al. (1998) on 29.99 March. Based on extrapolations of the light curve we claim that

We propose to improve the calibration of the Wind momentum - Luminosity Relationship of hot stars at solar metallicity by adding new objects with well determined distances, stellar parameters and wind momenta. We propose to acquire STIS low- resolution FUV spectra of O- and B-supergiants belonging to the same OB association to determine their

During September-October 1997, 21 three-component broadband seismometers were deployed on Stromboli Volcano at radial distances of 0.3-2.2 km from the active crater to investigate the source mechanisms of Strombolian explosions. In the 2-50 s band, the very-long period (VLP) signals associated with explosions are consistent with two stationary