We report the first deep UBV RI CCD photometry of 2460 stars in the field of two poorly studied OB associations Bochum 1 and Bochum 6. We selected 15 and 14 probable members in Bochum 1 and Bochum 6 respectively using photometric criteria and proper motion data of Tycho 2. Our analysis indicates variable reddening having mean value of E(B − V ) = 0.47±0.10 and 0.71±0.13 mag for Bochum 1 and Boc...

The Survey for Transiting Extrasolar Planets in Stellar Systems (STEPSS) project is a search for planetary transits in open clusters. In this paper, we analyze the STEPSS observations of the open cluster NGC 1245 to determine the variable star content of the cluster. Out of 6787 stars observed with V < 22, of which ∼ 870 are cluster members, we find 14 stars with clear intrinsic variability tha...

In this paper, we present a web-based system, termed ISOGA, that uses isochrones to perform geographical reachability analysis. An isochrone in a spatial network covers all space points from where a query point is reachable within given time constraints. The core of the system builds an efficient algorithm for the computation of isochrones in multimodal spatial networks. By joining isochrones w...

We have observed NGC 3603, the most massive visible H II region known in the Galaxy, with ANTU(VLT1)/ISAAC in the near-infrared (NIR) Js, H , and Ks-bands. Our observations are the most sensitive observations made to date of this dense starburst region, allowing us to investigate with unprecedented quality its low-mass stellar population. Our mass limit to stars detected in all three bands is 0...

We present color magnitude diagrams of four blue massive and compact star clusters in M31: G38, G44, G94, and G293. The diagrams of the four clusters reveal a well-populated upper main sequence and various numbers of supergiants. The U-B and B-V colors of the upper main sequence stars are used to determine reddening estimates of the different lines of sight in the M31 disk. Reddening values ran...

Some of the Galactic outer halo globular clusters are excellent tools to probe gravitational theories in the regime of weak accelerations (Baumgardt et al. 2005). The measurement of the line-of-sight velocity dispersion among stars in these clusters will differentiate between the validity of Newtonian dynamics (low velocity dispersion) and the possiblity of modified Newtonian dynamics (MOND) or...

We show that the open cluster Trumpler 20, contrary to the earlier findings, is actually an old Galactic open cluster. New CCD photometry and high-resolution spectroscopy are used to derive the main parameters of this cluster. At [Fe/H]=−0.11 for a single red giant star, the metallicity is slightly subsolar. The best fit to the color-magnitude diagrams is achieved using a 1.3 Gyr isochrone with...

We present a new method to compute stellar ages in Globular Clusters (GC) that is ten times more precise than the traditional isochrone fitting procedure. The method relies on accurate stellar evolutionary tracks and on photometry for GCs complete down to the main sequence, and it is based on counting number of stars in two different regions of the CMD: the red giant branch and the main-sequenc...

In this paper, we present the VI-CCD photometry of 11 unstudied clusters located in the bar of the Large Magellanic Cloud (LMC), as a part of a project aimed to infer the star formation history of this galaxy. We derive the ages of these clusters by means of isochrone fitting. Three close pairs of clusters are included in the sample, namely NGC 1903-SL 357, SL 349SL 353, SL 387-SL 385. We discu...

We review two new methods to determine the age of globular clusters (GCs). These two methods are more accurate than the classical isochrone fitting technique. The first method is based on the morphology of the horizontal branch and is independent of the distance modulus of the globular cluster. The second method uses a careful binning of the stellar luminosity function and determines simultaneo...