NGC 6811 is one of the four open clusters located in the Kepler spacecraft field of view. We obtained UBVRI photometry of the cluster on six nights (four of them photometric) with the 1.08m Hall and 1.83m Perkins telescopes at Lowell Observatory. The mean photometric precision ranges from better than 0.01mag in the V, B-V, V-R, and V-I indices among stars brighter than magnitude 15 to about 0.05mag for U-B at magnitude 18. We followed a Bayesian statistical approach using the Markov Chain Monte Carlo algorithm to determine the cluster reddening, distance, age, and iron content from a maximum-likelihood fit to stellar isochrones. Using the Yale-Yonsei isochrones, we derived E(B-V)=0.066+/-0.025, (m-M)_V_=10.13+/-0.19, age=1.06+/-0.19Gyr, and Z=0.012+/-0.004 ([Fe/H]=-0.18); with the Padova isochrones, we found E(B-V)=0.081+/-0.015, (m-M)_V_=10.31+/-0.11, age=0.94+/-0.08Gyr, and Z=0.012+/-0.002 ([Fe/H]=-0.20). The uncertainties include possible errors in the photometric zero points of +/-0.01mag, but do not include uncertainties in the models. Taking into account the differences between the two sets of models, we find the best estimate for the cluster parameters to be E(B-V)=0.074+/-0.024, (m-M)_V_=10.22+/-0.18, age=1.00+/-0.17Gyr, and Z=0.012+/-0.004 ([Fe/H]=-0.19).
We have obtained the first UBV(RI)C photoelectric light curves of the recently discovered eclipsing binary BD+66 1663 = GSC 4479 412 (P=7.04d, V=10.14). We have derived relative and absolute parameters of the binary, and analyzed the interstellar extinction towards the object. Though the star is located in the field of the young open cluster Be 59, we demonstrate that it is not a member.
We analyse CCD broad band (UBV(RI)c) photometric data obtained in the fields of the poorly studied open clusters NGC 2425 and NGC 2635. Both clusters are found to be of intermediate age thus increasing the population of open clusters known to be of the age of, or older than, the Hyades. More explicitly, we find that NGC 2425 is a 2.2Gyr old cluster, probably of solar metallicity, located at 3.5kpc from the Sun. NGC 2635 is a Hyades age (600Myr) cluster located at a distance of 4.0kpc from the Sun. Its Colour Magnitude Diagram reveals that it is extremely metal poor for its age and position, thus making it a very interesting object in the context of Galactic Disk chemical evolution models.
Ages derived from the low mass stars still contracting onto the main sequence often differ from ages derived from the high mass ones that have already evolved away from it. We investigate the general claim of disagreement between these two independent age determinations by representing UBVRI photometry of the young galactic open clusters NGC 2232, NGC 2516, NGC 2547 and NGC 4755, spanning the age range ~10-150Myr.
UBVRI H{alpha} CCD photometry has been obtained fro the young cluster NGC 2264. Using (R-H{alpha}) color, a measure of H{alpha} emission, we selected member stars in the pre-main sequence (PMS) stage.
We present CCD UBVI photometric and medium/high resolution spectroscopic observations obtained in the field of the previously unstudied dissolving open cluster candidates NGC 5385, NGC 2664 and Collinder 21. Our analysis is based on the discussion of star counts, photometry, radial velocity distribution, and proper motions available from the Tycho 2 catalogue (<I/259>). All three aggregates clearly emerge from the mean Galactic field, but, regrettably, the close scrutiny of proper motions and radial velocities reveals that we are not facing any physical group. Instead, what we are looking at are just chance alignments of a few bright unrelated stars. Our analysis casts some doubt on the Bica et al. (2001A&A...366..827B) criterion to look for Possible Open Cluster Remnants. It seems mandatory to define a better criterion to adopt for further investigations.
The three open clusters Be 15, Be 80 and NGC 2192 have been observed using CCD UBV(RI)C photometry at the San Pedro Martir Observatory, Mexico within the framework of our open-cluster survey. The fundamental parameters of interstellar reddening, distance and age have been derived, and also the metallicity for NGC 2192 (solar metallicity has been assumed for the other two).
We present UBVRI photometry of the open cluster NGC 2422 (age~10^8^yr) down to a limiting magnitude V=~19. These data are used to derive the Luminosity and Mass Functions and to study the cluster spatial distribution. By considering the color-magnitude diagram data and adopting a representative cluster main sequence, we obtained a list of candidate cluster members based on a photometric criterion.
Based on photometry of deep CCD frames of the central region of the OB cluster Berkeley 86, we derive the cluster mass function. The absence of current star formation, and the cluster's young age of about 6Myrs, leads to the conclusion that the initial mass function (IMF) and the current mass function are identical for stars with m<10m_{sun}_. In the range of 1.2-20m_{sun}_, an IMF with a slope of {GAMMA}=-1.3+/-0.3 is found. This value agrees well with other recent determinations of young clusters IMFs which are close to the classical Salpeter IMF with {GAMMA}=-1.35. Sections of the IMF of Berkeley 86 that are significantly steeper, or flatter, are most likely the result of a dip in the star's mass distribution in the range of 3.5-10m_{sun}_. Similar dips may have led to steep IMFs over narrow mass ranges, as reported in the literature for some other clusters. No sign for a low mass turn-over in the IMF of Berkeley 86 is found for masses extending down to 0.85 m_{sun}_.
We have carried out deep (V~21mag) UBVRI photometric study of the star cluster Stock 18. These along with archival Infrared data have been used to derive the basic cluster parameters and also to derive the basic cluster parameters and also to study the star for formation processes in and around the cluster region. The distance to the cluster is derived as 2.8+/-0.2kpc while its age is estimated as 6.0+/-2.0Myr. Present study indicates that interstellar reddening is normal in the direction of the cluster. The mass function slope is found to be -1.37+/-0.27 for the mass range 1<M/M_{sun}_<11.9. There is no evidence found for the effect of mass segregation in main-sequence stars of the cluster. A young stellar population with age between 1-2Myr have been found in and around the cluster region. The presence of IRAS and AKARI sources with MSX intensity map also show the youth of the Sh2-170 region.
