Esta tesis trata diversos aspectos de relacionados con el estudio de la todavía poco conocida fase de transición comprendida entre la Rama Asintótica de Gigantes y el estado de Nebulosa Planetaria. Para ello, hemos analizado varios tipos de objetos en esta corta fase evolutiva, incluyendo estrellas AGB/post-AGB y proto-nebulosas planetarias

The theory of the generation and transfer of polarized radiation, mainly developed for interpreting solar spectropolarimetric observations, allows us to reconsider, in a more rigorous and elegant way, a physical mechanism that has been suggested some years ago to interpret the high degree of polarization often observed in astronomical masers. This

We present Spitzer Space Telescope infrared photometric time series of the transiting extrasolar planet system TrES-1. The data span a predicted time of secondary eclipse, corresponding to the passage of the planet behind the star. In both bands of our observations, we detect a flux decrement with a timing, amplitude, and duration as predicted by

The disks of spiral galaxies are commonly thought to be truncated: the radial surface brightness profile steepens sharply beyond a certain radius (3-5 inner disk scale lengths). Here we present the radial brightness profiles of a number of barred S0-Sb galaxies with the opposite behavior: their outer profiles are distinctly shallower in slope than

We describe a newly discovered detached M dwarf eclipsing binary system. This system was first observed by the TrES network during a long-term photometry campaign of 54 nights. Analysis of the folded light curve indicates two very similar components orbiting each other with a period of 1.12079 +/- 0.00001 days. Spectroscopic observations with the

We present a near-infrared (K'-band) survey of 0.7 square degree area in the α Persei open cluster (age = 90 Myr, distance = 182 pc) carried out with the Omega-Prime camera on the Calar Alto 3.5-m telescope. Combining optical data (Rc and I_c) obtained with the KPNO/MOSA detector and presented in Stauffer et al. (1999) with the K' observations, a