Sunspot penumbrae harbor highly structured magnetic fields and flows. The moving flux tube model offers an explanation for several observed phenomena, e.g. the Evershed effect and bright penumbral grains. In this work, we present a generalized 3D model that embeds an arbitrarily shaped flux tube in a stratified magnetized atmosphere. The new model

Aims.The interpretation of globular cluster horizontal branch (HB) morphology is a classical problem that can significantly blur our understanding of stellar populations. Methods: .We present a new multivariate analysis connecting the effective temperature extent of the HB with other cluster parameters. The work is based on Hubble Space Telescope

We present N-body simulations of elliptical galaxy encounters into dry mergers to study the resulting unbound intergalactic stellar population, in particular that of the post-main-sequence stars. The systems studied are pairs of spherical galaxies without dark halos. The stellar content of the model galaxies is distributed into mass bins

We emphasize in this paper the importance of the UV range for our knowledge of massive stars and the fundamental role played by past and present space-based UV capabilities (IUE, HST, FUSE and others). Based on a review of the work developed in the last years and the state of the art situation for quantitative spectroscopy of massive stars, we

We present a detailed spectrophotometric analysis of the blue compact dwarf galaxy Mrk5 (NGC353, Haro3), based on deep BVRIJHK broad-band and H α narrow-band observations, and long-slit spectroscopy. The optical emission of the galaxy is dominated by a central young starburst, distributed in a bar-like shape, while an underlying component of older

The enormous energy output detected in many cores of galaxies is one of the key issues in the studies of galaxies and their evolution, notwithstanding several questions remain unsolved: Are accretion onto super-massive black holes and violent star formation just coevolving phenomena or necessary partners of the activity? How is the detailed physics