There are several hundred thousand R = 2000 stellar spectra reported in the final public release of the Sloan Digital Sky Survey (SDSS-I) and the continuation project SEGUE (Sloan Extension for Galactic Exploration and Understanding), which has completed roughly half of its scheduled set of observations to date. The stars in this sample were

We investigate the stellar populations in the star-forming ring of the luminous infrared galaxy NGC 7469. We use HST multiwavelength (UV through NIR) imaging complemented with new K-band ground-based long-slit spectroscopy, and mid-IR and radio maps from the literature. SEDs and evolutionary synthesis models have been used to characterize the star

Aims: We investigate the relationship between the photospheric magnetic field and the emission of the mid chromosphere of the Sun. Methods: We simultaneously observed the Stokes parameters of the photospheric iron line pair at 630.2 nm and the intensity profile of the chromospheric Ca II H line at 396.8 nm in a quiet Sun region at a heliocentric

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Aims:We calculate the dust emission expected at 3.43 and 3.53 μm if meteoritic (i.e. hydrogenated) nanodiamonds are responsible for most of the far-UV break observed in quasars. Methods: We integrate the UV flux that hydrogenated nanodiamonds must absorb to reproduce the far-UV break. Based on laboratory spectra of H-terminated diamond surfaces, we

We present a theoretical investigation on the influence of a deterministic magnetic field on the linear and circular polarization of the Na I, K I, and Ba II D2 lines. We describe the three ions by means of a three-level atomic model, and we take into account the hyperfine structure which is shown by some isotopes. We focus on the ``solar