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X-shooter is the first second-generation instrument for the ESO Very Large Telescope and will be installed in 2008. It is intended to become the most powerful optical & near-infrared medium-resolution spectrograph in the world, with a unique spectral coverage from 300 to 2500 nm in one shot. The X-shooter consortium members are from Denmark, France, Italy, The Netherlands and ESO., To appear in Proceedings ESO workshop on "Science with the VLT in the E-ELT era", Ed. A. Moorwood

Context: Knowledge of the age distribution of stars in young clusters and associations is crucial to constrain models of star formation. HR diagrams of different young clusters and associations suggest the presence of age spreads, but the influence of errors on the derived ages is still largely debated. Determination of lithium abundances in low-mass stars represents an alternative and robust way to infer stellar ages. Aims: We measured lithium in a sample of low mass members of the young (4-5 Myr) sigma Ori cluster with the main goal of investigating its star formation history. Methods: Using the FLAMES multi-object spectrograph on VLT/UT2, we obtained spectra of 98 candidate cluster members. The spectra were used to determine radial velocities, to infer the presence of Halpha emission, and to measure the strength of the Li 670.8 nm absorption line. Results: Using radial velocities, Halpha and Li, together with information on X-ray emission, we identified 59 high probability cluster members. Three of them show severe Li depletion. The nuclear ages inferred for these highly depleted stars exceed 10-15 Myr; for two of them these values are in good agreement with the isochronal age, while for the third star the nuclear age exceeds the isochronal one., Comment: 4 pages, 4 figures, Accepted for publication in A&A Letters

We present high-resolution Chandra HETGS X-ray spectra of the classical T Tauri star SU Aur. The quiescent X-ray emission is dominated by a 20-40 MK plasma, which contrasts strongly with the cool 3 MK plasma dominating the X-ray emission of the CTTS TW Hya. A large flare occurred during the first half of our 100 ks observation, and we have modelled the emitting plasma both during this flare and during the apparently quiescent periods. During the flare, an extremely high temperature plasma component (at least 60 MK) accounts for the bulk of the emission. There is an indication of the presence of Fe XXVI emission at 1.78 Angstrom, which is maximally formed at 130 MK., Comment: 4 pages, 6 figures. Proceedings paper for Cool Star 13 conference

NGC 3532 is a very rich southern open cluster of age ~200-350 Myr; it is therefore a good candidate to investigate the X-ray activity-age-rotation relationship at ages intermediate between the Pleiades and the Hyades, where, to our knowledge, X-rays studies exist for only one cluster (NGC 6475). We have performed an X-ray study of NGC 3532 using HRI observations retrieved from the ROSAT archive. The observations have a limiting sensitivity $L_{\mathrm x} \sim 4 \times 10^{28}$ erg sec$^{-1}$ in the center of the field. We detected ~50 X-ray sources above a $4 \sigma$ threshold, half of which have a known optical counterpart within 10 arcsec; 15 of the X-ray sources have at least one cluster member as optical counterpart. A comparison of NGC 3532 with the nearly coeval cluster NGC 6475 indicates that the former cluster is considerably X-ray underluminous with respect to NGC 6475. However, because of the existence of possible selection effects, additional X-ray and optical observations are needed before definitively concluding that the X-ray properties of NGC 3532 and NGC 6475 are significantly different., Comment: 6 pages, 3 figures, 3 tables, to appear in A&A

We present the analysis of the X-ray data of the young active star HD35850 obtained with ASCA and ROSAT. Our main goal was to see if there is a difference in the elemental abundances of active stars between young and more evolved objects. A two temperature plasma with subsolar abundances, of the order of Z = 0.15 - 0.3, is required to fit the SIS spectra. Similar results are obtained from a ROSAT PSPC observation. Metal abundances of 0.2 - 0.4 the solar value are required to fit both the ASCA and ROSAT data together. From a simultaneous SIS0+SIS1 spectral fit, with 2T plasma models and abundances free to vary in non-solar proportions, we find that, besides N, O and Ne for which we find very low values, all other elements have values relative to solar abundances around 0.2-0.3. These subsolar abundances are in line with those typically observed in more evolved, active stars like RS CVn and Algol-type binaries. The two temperature values required to fit the ASCA SIS spectra are about 0.5 and 1.0 keV. These temperatures, especially the higher one, are lower with respect to the values found for the RS CVn and Algol binaries or for the young star AB Dor, but higher than other single G/K stars. All our data show that this single, late F-type star is actually a very active source, indirectly confirming that this fast rotating star is probably a young object. In the simultaneous fit of the ASCA+ROSAT data, a third temperature is required. However this is not just an addition of a softer component, but is more a redistribution of the dominant temperatures. Indeed, the range spanned by the three temperatures, from 5 to 15 million degrees, is not very large., Comment: 10 pages, 5 tables and 3 figures. In press on A&A

We have compiled a catalog of late-type stars (F5-M) members of representative, young disk, stellar kinematic groups: the Local Association (20-150 Myr), Ursa Mayor group (300 Myr), Hyades supercluster (600 Myr), IC 2391 supercluster (35 Myr), and Castor moving group (200 Myr). Stars have been selected from previously established members of stellar kinematic groups based in photometric and kinematic properties as well as from candidates based in other criteria as their level of chromospheric activity, rotation rate, lithium abundance. Precise measurements of proper motions and parallaxes taken from Hipparcos Catalogue, and published radial velocity measurements are used to calculate Galactic space motions (U, V, W) in order to determine the membership of the selected stars to the different stellar kinematic groups.