We present abundance measurements, based on high-resolution optical spectroscopic data obtained with the Ultraviolet and Visual Echelle Spectrograph mounted on Kueyen (Very Large Telescope UT2), for ten stars in the extended blue horizontal branch of the Galactic globular cluster NGC 1904 (M79). In agreement with previous findings for other

UV, optical, and near-IR spectra of Vega have been combined to test our understanding of stellar atmospheric opacities and to examine the possibility of constraining chemical abundances from low-resolution UV fluxes. We have carried out a detailed analysis assuming local thermodynamic equilibrium (LTE) to identify the most important contributors to

We report the results of a photometric search for giant stars associated with the cores of four high-velocity clouds (HVCs)-two of which are compact HVCs-using the Las Campanas du Pont 2.5 m and Cerro Tololo Blanco 4 m telescopes in combination with a system of filters (Washington M, T2+DDO51) useful for identifying low surface gravity, evolved

Using the 770 ks XMM-Newton survey of the Lockman Hole field in combination with extensive optical identifications of the AGN population, we derive an average rest-frame spectrum of AGN types-1 and 2. The most prominent feature in the averaged spectrum is a strong fluorescent Fe line. In both type-1 and type-2 AGN, a clear relativistic line profile

BPM 37093 is the only hydrogen-atmosphere white dwarf currently known which has sufficient mass (~1.1 M&sun;) to theoretically crystallize while still inside the ZZ Ceti instability strip (Teff˜12 000 K). As a consequence, this star represents our first opportunity to test crystallization theory directly. If the core is substantially crystallized

We present deep multiband (F435W, F625W, and F658N) photometric data of the globular cluster ω Cen collected with the Advanced Camera for Surveys on board the Hubble Space Telescope. We identified in the (F435W - F625W, F435W)-plane more than 2000 white dwarf (WD) candidates using three out of nine available pointings. Such a large sample appears