The Active Phasing Experiment (APE) has been used by ESO to gain experience in controlling segmented primary mirrors in preparation for the European Extremely Large Telescope. The experiment tested various phasing techniques and explored their advantages and limitations. Four optical phasing sensors were developed using different techniques — a

We present Integral Field Unit GMOS-IFU data of the compact H II galaxy UM 408, obtained at the Gemini South telescope, in order to derive the spatial distribution of emission lines and line ratios, kinematics, plasma parameters, and oxygen abundances as well the integrated properties over an area of 3''×4farcs4 equivalent with ~750 pc × 1100 pc

We show a selection of high-sensitivity spectropolarimetric observations obtained over the last few years in the Ba II D_2-line with the Zürich Imaging Polarimeter (ZIMPOL) attached to the Gregory Coudé Telescope of IRSOL. The measurements were collected close to the solar limb, in several regions with varying degree of magnetic activity. The

Available from the Minor Planet Center.

We present some results obtained from the synthesis of Stokes profiles in small-scale flux sheets with propagating MHD waves. To that aim, 2D flux sheets showing internal structure have been excited with 5 min period drivers, allowing non-linear waves to propagate inside the magnetic structure. The observational signatures of these waves in Stokes

The spectral energy distributions for pure-hydrogen (DA) hot white dwarfs can be accurately predicted by model atmospheres. This makes it possible to define spectrophotometric calibrators by scaling the theoretical spectral shapes with broad-band photometric observations - a strategy successfully exploited for the spectrographs onboard the Hubble