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

A spectroscopic study of the Trapezium Cluster stars in the Orion Nebula is presented. We determine the stellar parameters of the two B0.5V stars theta(1}_{) Ori A and D. The variable spectral features of theta(1}_{) Ori C are studied, and some consequences on the modeling of the stellar atmosphere are considered.

The redshift distribution of flat-spectrum radio sources with 5 GHz flux densities S5>~5 mJy is a key component in using current radio lens surveys to probe the cosmological model. We have constructed the first flat-spectrum radio sample in the flux density range 3-20 mJy. Our new sample has 33 sources; we have determined the redshifts of 14 of