Using photometric and redshift data for the Virgo and Coma Clusters, we present evidence for a correlation between the light concentration of elliptical galaxies (including dwarf ellipticals) and the local three-dimensional (i.e., nonprojected) density of the clusters: more concentrated ellipticals are located in denser regions. The null hypothesis

A bright X-ray transient was detected by Chandra on 2002 June 2 with a series of 5 HRC-I snapshots. The new source CXOU J004154.6+405648 (R.A.=00h41m54s.64, Dec.=+40d56m48s.0, +/- 1", J2000) is discovered at a luminosity (0.3-10 keV) of 1.5 x 1038 erg/s (assuming an absorbed power-law model with photon index = 2 and NH = 1021 cm-2 at a distance of

We undertook a study of the star formation and chemical enrichment history of the Fornax dSph galaxy. We used the VLT with FORS1 to obtain photometry reaching the oldest main-sequence turnoffs and Ca II triplet spectroscopy of a sample of red giant branch stars in the same fields. The observations and the main results are described.

The kinematics and physical conditions of the bipolar planetary nebula M 2-48 are analysed from high and low dispersion long-slit spectra. Previous CCD narrow-band optical observations have suggested that this nebula is mainly formed by a pair of symmetric bow-shocks, an off-center semi-circular shell, and an internal bipolar structure. The bipolar

The heat flow and temperature structure within and surrounding a magnetic flux tube stored in mechanical equilibrium in a stellar convection zone are considered. The stationary thermal equilibrium state is determined through the analytical solution of a two-dimensional heat diffusion problem for an infinitely long cylinder with different thermal

As a part of a project devoted to the study of the Ursa Minor dwarf spheroidal (dSph) galaxy, the star formation history of the galaxy is presented. The analysis uses wide-field photometry, encompassing about 1°×1° (the total covered area being 0.75 deg2), which samples the galaxy out to its tidal radius. Derivation of the star formation history