We report on high angular resolution, high-precision spectropolarimetric measurements of a decaying sunspot. The spot gradually lost its penumbra during the course of 3 days. In the late stages of evolution, where the only remnant of the spot is a naked umbra, we find small-scale inhomogeneities in the magnetic canopy surrounding it. The

We present the results of long-slit spectroscopy, in several positions, of the Orion Nebula. Our goal is to study the spatial distributions of a large number of nebular quantities, including line fluxes, physical conditions, and ionic abundances, at a spatial resolution of about 1". In particular, we have compared the O++ abundance determined from

We present a rapid timing analysis of VLT (optical) and RXTE data of the Galactic black hole GX 339-4 in the low/hard state in June 2007, soon after emerging from outburst. Both optical and X-ray power density spectra are qualitatively similar with QPO-like feature or a break around 0.05-0.1 Hz. A cross-correlation function (CCF) analysis finds no

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 continuing 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 targeted

The Zeeman pattern of Mn I lines is sensitive to hyperfine structure (HFS), and because of this, they respond to hectogauss magnetic field strengths differently than the lines commonly used in solar magnetometry. This peculiarity has been employed to measure magnetic field strengths in quiet-Sun regions, assuming the magnetic field to be constant

The proper motion measurements for 143 previously known L and T dwarfs are presented. From this sample we identify and discuss eight high-velocity L dwarfs. We also find four new wide common proper motion binaries/multiple systems. Using the moving cluster methods we have also identified a number of L dwarfs that may be members of the Ursa Major