We present results of our combined X-ray and optical study of NGC 2451, which actually consists of two different stellar clusters situated along the same line-of-sight at distances of 190 and 360 pc, respectively. Based on ROSAT X-ray observations and on our extensive optical CCD BVR-photometry we are able to identify 113 stars down to spectral

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

We discuss, in terms of particle acceleration, the results from optical observations with ESO's Very Large Telescope aimed at the detection of the optical counterparts of radio hot spots. To select the targets, we adopted criteria based on theoretical expectations and obtained an unprecedented 70% detection rate. Our results strongly suggest that

We present a detailed spectroscopic investigation, spanning four winters, of the asymptotic giant branch (AGB) star IRAS 02091+6333. Zijlstra & Weinberger (cite{ZW}) found a giant wall of dust around this star and modelled this unique phenomenon. However their work suffered from the quality of the optical investigations of the central object. Our

We present simultaneous and continuous observations of Hα, Hβ, ion{Na}{1} D1, D2, ion{He}{1} D3 and ion{Ca}{2} H & K lines of the chromospherically active binary HR 1099. We have observed HR 1099 for more than 3 weeks almost continuously and monitored two flares. An increase in Hα and ion{Ca}{2} H & K, Hβ and ion{He}{1} D3 and a strong filling-in

We present 26 minima times of 11 eclipsing binaries, observed between 1996 and 1999.