RX J1211+2242 is an optically faint (B~=19.2mag) but X-ray bright (f2-10keV=5×10-12ergscm-2s-1) active galactic nucleus (AGN) that has been shown to be a BL Lac object at redshift z=0.455. The ROSAT X-ray, Calar Alto optical, and NRAO VLA Sky Survey (NVSS) radio data suggest that the peak of the synchrotron emission of this object is at energies as

We present the results of an analysis of our infrared light curves of the Algol-type binary AI Draconis in the J, H and K bands, and of published light curves in the B, V and Strömgren uvby bands, together with spectra obtained by us. The analysis of the light curves was carried out using a code based on ATLAS model atmospheres and Roche geometry

We report rapid near-infrared observations of GRB 020819. We find that any afterglow was fainter than K'=19 only 9 hrs after the burst. We discuss if extinction by cosmic dust in the GRB host galaxy can explain the faintness of this afterglow.

We have calculated the structural models of sdB stars and their corresponding theoretical frequencies needed to carry out an asteroseismological analysis.

We obtained moderate/low resolution spectroscopy (2/5 AA FWHM) of the microquasar candidate MCQC J162847-4152 (hereafter J1628) on 2003 May 5/6/13 (UT) and June 22/23/25 with the B&C spectrograph mounted on the 6.5-m Baade and Clay telescopes at LCO. In addition, high resolution spectra (R~27000 and 36000 in the blue and red respectively) were

We report the results of a high-resolution spectroscopic survey of all the stars more luminous than M_V = 6.5 mag within 14.5 pc from the Sun. The Hipparcos catalog's completeness limits guarantee that our survey is comprehensive and free from some of the selection effects in other samples of nearby stars. The resulting spectroscopic database