DQ white dwarfs have Teff values below 13000 K and are characterized by the presence of trace amounts of carbon in their helium-rich atmospheres. The wide range of surface carbon abundances they exhibit could be reflecting the existence of hydrogen-deficient white dwarfs with a variety of evolutionary history and formation processes. The aim of

Abundances of oxygen in two ultra-metal-poor giants have been derived from measurements of the oxygen triplet at 7771-5Å in the near-IR performed in high-resolution and high S/N ratio spectra obtained with KeckI/HIRES. A detailed non-LTE analysis of Fe lines has been carried out for our targets providing more reliable stellar parameters and

The Sloan Digital Sky Survey (SDSS) is collecting photometry and intermediate resolution spectra for ˜105 stars in the thick-disk and stellar halo of the Milky Way. This massive dataset can be used to infer the properties of the stars that make up these structures, and considerably deepen our vision of the old components of the Galaxy. We devise

Two time series, taken simultaneously in the G-band and the blue continuum, corrected for instrumental and atmospheric degradation using the method of phase diversity, are employed to study the motions of granules and G-band bright points (GBPs) in the moat of an old regular sunspot. Centres of diverging horizontal motions, identified with families

The Nuker model, when applied to the inner regions of ``core'' galaxies, is shown to produce systematic biases in the determination of the core ``break-radii''. These radii can easily be (and often have been, see Trujillo et al. 2003) over-estimated by more than 100%. Moreover, due to curvature in the outer profiles of early-type galaxies (i.e

The Ca II triplet is one of the most frequently measured features for deriving stellar metallicities from moderate resolution spectroscopy of red giants in old and metal poor systems. With the advent of 8m class telescopes, this indicator becomes of invaluable help in deriving metallicities for large samples of faint stars in the Local Group, and