We investigate the structure in depth of a sunspot penumbra by means of the inversion code of the radiative transfer equation proposed by Ruiz Cobo & del Toro Iniesta (1992), applied to a set of filtergrams of a sunspot, scanning the Fe I line at 5576.1 A, with a sampling interval of 30 mA, from -120 to 120 mA from line center (data previously

We examine the influence of non-adiabatic effects on the modes of an isothermal stratified magnetic atmosphere. We present new solutions for magneto-acoustic-gravity (or MAG) waves in the presence of a radiative heat exchange based on Newton's law of cooling. An analytic expression for the dispersion relation is derived, which allows the effect of

We have examined the wind momentum problem of O-type stars in the Galaxy. It is shown that the discrepancy between theoretical and empirical mass loss rates and terminal velocities can be reversed by using recently updated values of force multiplier parameters. With these new values, the momentum problem found by former investigators is reversed so

We present contemporaneous optical and infrared (IR) photometric observations of the Type IIn SN 1998S covering the period between 11 and 146d after discovery. The IR data constitute the first ever IR light curves of a Type IIn supernova. We use blackbody and spline fits to the photometry to examine the luminosity evolution. During the first 2-3

Not Available

We have carried out an optical follow-up of twelve ROSAT discovered candidate members of the Coma Berenices open cluster. VRI photometry and low resolution ( ~ 3 Å) spectroscopy in the range 3800-7000 Åwere performed to obtain colour-magnitude diagrams, proper motions, spectral types, chromospheric activity levels and radial velocities that allow