We present the results of 3632 astrometric CCD-measurements of 314 visual double stars performed with the 26-inch refractor of the Pulkovo observatory in 2003-2007. Angular separations (rho) and position angles (theta) are provided. Mean values of standard errors are 0.009" in rho and 0.40(deg)/rho in theta, where rho is the separation in arcseconds.
We present new astrometric and photometric data for 253 visual double stars of the "intermediate" class, i.e. with angular separations in the range 1 to 15 arcsec. The multi-colour observations were obtained in 1992-94 as part of the ESO Key Programme "Visual Double Stars" performed at La Silla Observatory (Chile). Differential magnitudes and colours have been secured in a systematic way while component magnitudes and colour indices have been determined in the V and I passbands of the Cousins standard system in good photometric conditions only. Internal and mean external errors are respectively smaller than 0.01mag and a few hundred of a magnitude (0.02 to 0.03mag). Relative positions are obtained as a by-product with internal errors of the order of 0.006arcsec in angular separation and 0.08{deg} in position angle. Final accuracies are thoroughly discussed: we illustrate the overall excellent quality of the data and estimate the quality degradation for angular separations barely larger than the width of the seeing disk.
Within the sample of six young open clusters (NGC 1502, NGC 3105, Stock 16, NGC 6268, NGC 7235 and NGC 7510) we have investigated 1753 objects using the narrow band, three filter Delta a photometric system resulting in the detection of eleven bona-fide magnetic chemically peculiar (CP) stars and five Be or metal-weak stars. The results for the distant cluster NGC 3105 is most important because of the still unknown influence of the global metallicity gradient of the Milky Way. These findings confirms that CP stars are present in open clusters of very young ages (logt>=6.90) at galactocentric distances up to 11.4kpc. For all programme clusters the age, reddening and distance modulus were derived using the corresponding isochrones. Some additional variable stars within Stock 16 could be identified by comparing different photometric studies.
The M33 galaxy is a nearby, relatively metal-poor, late-type spiral. Its proximity and almost face-on inclination means that it projects over a large area on the sky, making it an ideal candidate for wide-field CCD mosaic imaging. Photometry was obtained for more than 106 stars covering a 74'x56' field centered on M33. Main-sequence, supergiant branch, red giant branch, and asymptotic giant branch (AGB) populations are identified and classified based on broadband V and I photometry. Narrowband filters are used to measure spectral features allowing, the AGB population to be further divided into C and M star types. The galactic structure of M33 is examined using star counts, color-color, and color-magnitude-selected stellar populations. We use the C to M star ratio to investigate the metallicity gradient in the disk of M33.
We present a photometric study of the globular clusters (GCs) in the giant elliptical galaxy M60 in the Virgo Cluster, based on deep, relatively wide field Washington CT_1_ CCD images. The CMD reveals a significant population of GCs in M60 and a large number of young luminous clusters in NGC 4647, a small companion spiral northwest of M60. The color distribution of the GCs in M60 is clearly bimodal, with a blue peak at (C-T_1_)=1.37 and a red peak at (C-T_1_)=1.87. We derive two new transformation relations between the (C-T_1_)_0_ color and [Fe/H] using the data for the GCs in our Galaxy and M49. Using these relations, we derive the metallicity distribution of the GCs in M60, which is also bimodal: a dominant metal-poor component with center at [Fe/H]=-1.2, and a weaker metal-rich component with center at [Fe/H]=-0.2. We estimate the total number of the GCs in M60 to be 3600+/-500 and the specific frequency to be S_N_=3.8+/-0.4.
We present BV and u'g'r'i' CCD photometry of the central region of NGC 2482. We also present BVu'g' CCD photometry of five clusters that have been poorly studied in the past: Ruprecht 42, Ruprecht 51, Ruprecht 153, Ruprecht 154, and AH03 J0748-26.9, which to our knowledge has not been studied before. Using a global optimization technique that eliminates much of the subjectivity previously inherent in main-sequence fitting studies, we obtain values of the distances, ages, and metallicities of the clusters, with robust estimates of the uncertainties of these fundamental parameters. Four of our clusters are less than ~1.3kpc beyond the Sun's distance from the Galactic center and have essentially solar metallicity. The metallicities of those clusters more distant from the Galactic center are consistent with a 0.3dex step to lower [Fe/H] found in other studies.
B and V band CCD photometry is used to study 33 cluster and nine field RR Lyrae variables near the LMC cluster, NGC 2257. It is found that the mean magnitudes for the two groups differ by 0.17 mag. The cluster and field variables both have an Fe/H abundance ratio of -1.8+/-0.1. The results are compared used to compare NGC 2257 with galactic globular clusters, showing that NGC 2257 is indistinguishable from its local counterparts.
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