The solar atmosphere has been studied for decades by means of observations, theory and numerical simulations. However, due to its complexity, it is difficult to fully understand all the phenomena taking place in the atmosphere. Starting from the photosphere up to the corona, the solar atmosphere is strongly stratified and the magnetic fields

El objetivo de esta tesis es el estudio sismológico de estrellas de tipo solar en sistemas binarios eclipsantes. Las estrellas binarias son los únicos sistemas en los que podemos conocer los parámetros globales de las estrellas que los componen, tales como masa y radio, con una buena precisión. Conocer estas propiedades es importante a la hora de

We report on the analysis of the Chandra-ACIS data of O, B, and WR stars in the young association Cyg OB2. X-ray spectra of 49 O-stars, 54 B-stars, and 3 WR-stars are analyzed and for the brighter sources, the epoch dependence of the X-ray fluxes is investigated. The O-stars in Cyg OB2 follow a well-defined scaling relation between their X-ray and

As part of our ongoing NTT SoFI survey for variability in young free-floating planets and low-mass brown dwarfs, we detect significant variability in the young, free-floating planetary-mass object PSO J318.5–22, likely due to rotational modulation of inhomogeneous cloud cover. A member of the 23 ± 3 Myr β Pic moving group, PSO J318.5–22 has Teff =

Ultra high energy photons and neutrinos are carriers of very important astrophysical information. They may be produced at the sites of cosmic ray acceleration or during the propagation of the cosmic rays in the intergalactic medium. In contrast to charged cosmic rays, photon and neutrino arrival directions point to the production site because they

We report results obtained from a systematic analysis of X-ray lags in a sample of black hole X-ray binaries, with the aim of assessing the presence of reverberation lags and studying their evolution during outburst. We used XMM-Newton and simultaneous Rossi X-ray Timing Explorer (RXTE) observations to obtain broadband energy coverage of both the