Esta tesis presenta los análisis cuantitativos de espectros ópticos y UV de una muestra de estrellas supergigantes de tipo B en la Vía Láctea, M33 y NGC300, con objeto de determinar los parámetros fundamentales, así como sus composiciones químicas y comparar los resultados obtenidos con las predicciones de los modelos de evolución estelar y

High-altitude wind has been recently proposed as an important parameter to be taken into account for astronomical site selection. We present here comprehensive and reliable statistics for wind speeds at the 200 mbar (v200 hereafter) pressure level (approximately 12 km above the Canary Islands) based on long-term climate diagnostics archive and

A detailed study of two consecutive bright points observed simultaneously with the Coronal Diagnostic Spectrometer (CDS), the Extreme ultraviolet Imaging Telescope (EIT) and the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO) is presented. The analysis of the evolution of the photospheric magnetic features and

We have tested Very Small Array (VSA) observations of three regions of sky for the presence of non-Gaussianity, using high-order cumulants, Minkowski functionals, a wavelet-based test and a Bayesian joint power spectrum/non-Gaussianity analysis. We find the data from two regions to be consistent with Gaussianity. In the third region, we obtain a 96

We present radial and rotation (v sin i) velocity measurements from UVES+VLT high resolution spectra of 61 stars in the blue horizontal branches (HB) of the Galactic globular clusters NGC 1904 (M 79), NGC 2808, NGC 6093 (M 80) and NGC 7078 (M 15). The data reduction and the velocity determination, based on cross-correlation techniques, are

We present a search for rings or arcs in the haloes of planetary nebulae (PNe). We discovered such structures in eight PNe, tripling the sample of PNe with known rings. This shows that, contrary to what was believed to date, the occurrence of mass loss fluctuations with timescales of 102-103 yrs at the end of the asymptotic giant branch phase (AGB)