Volume 12, Issue 3

Spectral and luminosity classes, absolute magnitudes, color excesses, interstellar extinctions and distances are determined for 98 stars down to 18 mag in the Barnard 1 dark cloud belonging to the Per OB2 association. The classification of stars is based on their photoelectric photometry in the Vilnius seven-color photometric system. The extinction vs. distance diagram exhibits the presence of two dust layers at 150 and 230 pc distances. The distance of the first cloud, which gives an extinction Ay of 0.3 mag, coincides with the distance of the Taurus dark cloud complex. The second cloud with much larger extinction is about at the same distance as the clouds in the direction of the nearby objects: reflection nebula NGC 1333 and open cluster IG 348.

Seven-color photometry in the Vilnius system has been obtained for 420 stars down to V = 16 mag in the area containing the overlapping open clusters NGC 1750 and NGC 1758 in Taurus. Spectral and luminosity classes, color excesses, interstellar extinctions and distances are given for 287 stars. The classification of stars is based on their reddening-free Q-parameters. 18 stars observed photoelectrically were used as standards. The extinction vs. distance diagram exhibits the presence of one dust cloud at a distance of 175 pc which almost coincides with a distance of other dust clouds in the Taurus complex. The clusters NGC 1750 and NGC 1758 are found to be at the same distance of ~760 pc and may penetrate each other. Their interstellar extinction A V is 1.06 mag which corresponds to E B-V = 0.34 mag.

R-N classification of 187 faint carbon stars is based on the classical criteria adjusted to the yellow-red spectral region, with two new criteria added - the ratios of the red CN bands 6206/6332 (Å) and 6478/6631 (Å).

High-resolution spectra in the NaI D-line region for tar­get stars with R Coronae Borealis type variability are analyzed. Two types of relations between light weakening and equivalent widths of circumstellar lines are found, one of them being considerably different from a similar relation for the interstellar medium.

Photoelectric seven-color photometry in the Vilnius medium-band, system is obtained for 87 stars down to V≃13.0 in the Kiev proper motion field KA10 [l = 137°, b = -59°]. The size of the field is 1.4 square degrees. For each star, photometric spectral type, absolute magnitude, metallicity, and color excess due to interstellar reddening have been determined. These data, together with previous Vilnius photometry obtained in other seven KA fields at high Galactic latitudes, will be combined with radial-velocity measurements and available proper motions to yield space velocities and to investigate kinematical and chemical properties of the Galactic disk in the direction perpendicular to the Galactic plane.

The motion of test bodies in a Quasi-Newtonian potential is examined. Main attention is paid to the qualitative classification of all possible trajectories.

The paper deals with the motion of test bodies in a Quasi-Newtonian potential for which the expressions corresponding to the effects of General Relativity are found. It is impossible to choose the values of parameters of the potential which could be in a quantitative accordance with the effects predicted by General Relativity.