Flares and X-ray jets on the Sun arise in active regions where magnetic flux emerges from the solar interior amd interacts with the ambient magnetic field. The interactions are believed to occur in electric current sheets separating regions of opposite magnetic polarity. The current sheets located in the corona or upper chromosphere have long been

We are using the McDonald 2.7m and ESO 1.52m telescopes to obtain spectra of nearby stars at high-resolution, high S/N, and with complete optical coverage. The sample includes all stars in the Hipparcos catalog brighter than MV = 6.5 (˜ K2 V) within a 12770 pc3 sphere centered at the Sun. The survey is 78 % complete. The database will be publicly

The analysis of emission line region of Seyfert 1 galaxy Mrk 817 is presented. We found that emission line region in Mrk 817 is very complex. Moreover, the Narrow Line Region shows complex structure. The spectral line shapes of Mrk 817 indicates at least three kinematically separated regions, one (or more) which emits the broad line component (V

We describe the results of a search for transit-like events caused by giant planets occulting stars in the old, metal-rich open cluster NGC 6791 based on BVI-colour photometry from eight nights of observations with the 2.54 m Nordic Optical Telescope. To extract the light curves we have used both PSF photometry (DAOPHOT) and the difference imaging

Light curves and images of 67P/Churyumov-Gerasimenko are presented for the 2002-2003 apparition based on amateur CCD monitoring using a standardised method to produce consistent photometry in Johnson-Kron-Cousins system. Multiaperture data shows a large outburst at perihelion during which dust production increased by a factor of 2 to give a peak

We explain the linear polarization of the Ca ii infrared triplet observed close to the edge of the solar disk. In particular, we demonstrate that the physical origin of the enigmatic polarizations of the 866.2 and 854.2nm lines lies in the existence of atomic polarization in their metastable 2D3/2 , 5/2 lower levels, which produces differential