Aims: Using new Chandra X-ray observations and existing XMM-Newton X-ray and Hubble far ultraviolet observations, we aim to detect and identify the faint X-ray sources belonging to the Galactic globular cluster NGC 2808 in order to understand their role in the evolution of globular clusters. Methods: We present a Chandra X-ray observation of the

Context: The connection of cluster mergers with the presence of extended, diffuse radio sources in galaxy clusters is still debated. An interesting case is the rich, merging cluster Abell 520, containing a radio halo. A recent gravitational analysis has shown in this cluster the presence of a massive dark core suggested to be a possible problem for

Context: The young σ Orionis cluster is an important location for studying the formation and evolution of stars, brown dwarfs, and planetary-mass objects. Its metallicity, although it is a fundamental parameter, has not been well determined yet. Aims: We present the first determination of the metallicity of nine young late-type stars in σ Orionis

The accreting millisecond X-ray pulsar SAX J1808.4-3658 recently exhibited another outburst in September and October 2008 (ATel #1728). During this outburst, on 2008 Oct 2, we obtained a ~40 ks observation with Suzaku. The XIS detectors were operated in 1/4 window mode, with 1 sec burst, leading to a good time exposure of 21 ks for the XIS 0, 1 and

Context: Current atmospheric models cannot reproduce some of the characteristics of the transition between the L dwarfs with cloudy atmospheres and the T dwarfs with dust-depleted photospheres. It has been proposed that a majority of the L/T transition brown dwarfs could actually be a combinaison of a cloudy L dwarf and a clear T dwarf. Indeed

We present observations for three star clusters, Kron 11, Kron 63 and NGC 121, in the Small Magellanic Cloud. We have studied their structure and derived their fundamental parameters by means of their luminosity functions, their colour magnitude diagrams and the Padova suite of isochrones. NGC 121 is a well-studied object, for which we confirm