We present an RI photometric survey covering an area of 430 arcmin2 around the multiple star sigma Orionis. The observations were conducted with the 0.8 m IAC-80 Telescope at the Teide Observatory. The survey limiting R and I magnitudes are 22.5 and 21, and completeness magnitudes 21 and 20, respectively. We have selected 53 candidates from the I

Here we report on the properties of the star forming factory, in which the continuous creation of stars results into a highly concentrated, massive (globular cluster-like) stellar system. We show that under very general conditions a large-scale gravitational instability in the ISM, that triggers the collapse of a massive cloud, leads with the aid

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We present 45 photoelectric minima observations of 20 eclipsing binaries.

We have characterized the physical properties (electron temperature, density and metallicity) of the ionized gas and the ionizing population (age, metallicity and presence of Wolf-Rayet stars) in the Lynx arc, an HII galaxy at z= 3.36. The ultraviolet doublets (i.e. CIII], SiIII] and NIV) imply the existence of a density gradient in this object

The unprecedented spatial resolution of Chandra is allowing reliable identifications of the counterparts of M31 X-ray sources at other wavelengths. Comparisons with Hubble Space Telescope data, recent ground-based Local Group Survey data, and Very Large Array radio data reveal many interesting objects. These include newly-resolved X-ray/optical