We present three-dimensional numerical calculations of superbubbles evolving in a two-component interstellar medium composed of small diffuse clouds and a low-density intercloud medium. Cold H I clouds with internal densities n ˜ 10 cm-3 and radii Rcl = 3-5 pc were assumed to be embedded in a warm plane-stratified intercloud medium. The fraction of

Photon-counting techniques have been applied to a study of the movement of the image of an unresolved star at the 50 cm telescope of the Royal Academy of Sciences, at the Roque de los Muchachos Observatory. The temporal autocorrelation function of such movement has been computed, the results are discussed in terms of atmospheric turbulence and in

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A 50 min time series of one-dimensional slit-spectrograms, taken in quiet sun at disk centre, observed at the German Vacuum Tower Telescope (Observatorio del Teide), was used to study the global and spatial variations of different line parameters. In order to determine the vertical structure of the photosphere two lines with well separated

We present time-resolved optical spectroscopy and photometry, and far-ultraviolet spectroscopy of HS 0728+6738, a cataclysmic variable discovered in the Hamburg Quasar Survey. We show that the system is a new eclipsing member of the SW Sex class of CVs with an orbital period of 3.21 h. We derive an orbital inclination of ˜ 85 ± 4° from the average

Several works have recently shown that there is an important extra line-broadening (usually called macroturbulence) affecting the spectra of O and B Supergiants that adds to stellar rotation. So far, the only (very recent) physical explanation for the appearance of macroturbulence relates to oscillations. This is a plausible explanation, but no