The point spread function of a segmented aperture is seriously affected by the misalignment of the segments. Stringent requirements apply to position sensors and their calibration. The Active Phasing Experiment (APE) will be a technical instrument aimed at testing possible phasing techniques for a European Giant Optical Telescope (EGOT) in a

This paper presents a method to determine how much detail of the height stratification of atmospheric parameters can be retrieved from the inversion of spectral lines (and their polarization profiles, when available) via χ2-minimization algorithms. An a priori analysis of the response functions and their correlations permits an evaluation of the

A prototype system for the Permanent All Sky Survey (PASS) project is presented. PASS is a continuous photometric survey of the entire celestial sphere with a high temporal resolution. Its major objectives are the detection of all giant-planet transits (with periods up to some weeks) across stars up to mag 10.5, and to deliver continuously

Young stellar bars in disk galaxies experience a vertical buckling instability that terminates their growth and thickens them, resulting in a characteristic peanut/boxy shape when viewed edge-on. Using N-body simulations of galactic disks embedded in live halos, we have analyzed the bar structure throughout this instability and found that the outer

Early-type galaxies are thought to be among the oldest known stellar systems, and as such have experienced the full diversity of evolutionary mechanisms at work in the universe. They are crucial laboratories for understanding how galaxies form and evolve from early epochs until the present day. A key aspect of unlocking their fossil evidence is by

We present time-resolved optical spectroscopy and photometry, and far-ultraviolet spectroscopy of HS 0728+6738, a cataclysmic variable discovered in the Hamburg Quasar Survey. We show that the system is a new eclipsing member of the SW Sex class of CVs with an orbital period of 3.21 h. We derive an orbital inclination of ˜ 85 ± 4° from the average