The results of a UBVR photometric study in the field of the open cluster IC 1311 are presented. A comparison with previously published results on NGC 7044, based on measurements secured during the same observing run, leads to a self-consistent constraints to the parameters of the cluster. The location of selected samples of giant and unevolved

An international collaboration of fourty scientists have been involved in multifrequency observations of the blazar OJ 287, as well as of a few other complementary objects, taken both photometrically and spectroscopically. We present the optical light curve of OJ 287 obtained between the fall of 1993 through the present. Over 1200 photometric

We present a study of high-velocity gas in the direction of 13 halo sub-dwarfs located at absolute value of z approximately equals 0.5-2 kpc and of 8 early-type stars in the Galactic disk at d approximately equals 1-4 kpc. For each line of sight of our sample we collected Ca II and Na I absorption spectra with the 2.5-m Isaac Newton Telescope at La

We present new evidence against the universality of the de Vaucouleurs r^1/4^ law, considered to be the best empirical formula for fitting the light profiles of elliptical galaxies, through the analysis of the properties of the (D_n_/A_e_)-_e_ diagram for a volume-limited sample of early-type galaxies that are members of the Virgo and Fornax

Assuming that photoionization is the self-limiting process for continued star formation, we estimate the maximum number of massive (OB) stars that can form within a molecular cloud. The most efficient cloud destruction mechanism in the early stages of H II region evolution is the evaporation of the cloud by stars located near the cloud boundary

We combine a number of powerful mathematical techniques to produce an effective method for treating multidimensional radiative transfer problems in complex atomic models without assuming local thermodynamic equilibrium (LTE). The approach is so efficient that multilevel two-dimensional (2D) modeling can now be performed with no more than a