|The Optical Gravitational Lensing Experiment. Variable Stars in the Field of Open Cluster NGC6259|
We present the results of a search for variable stars in the field ofNGC6259. Altogether 85 variable stars have been discovered. 36 of themare eclipsing systems. This group contains 13 EA, 2 EB and 21 EW-typestars. Light curves of two variable stars resemble those of Miras. Theremaining 47 variable stars detected in the field of this open clusterare most probably highly obscured red giants (OSARG, irregular). For alldetected variable stars we provide their light curves, preliminaryclassification, discussion on the possible cluster membership,equatorial coordinates, finding charts and periods when possible.
|First estimates of the fundamental parameters of the relatively bright Galactic open cluster NGC 5288|
In this paper we present charge-coupled device (CCD) images in theJohnson B and V and Kron-Cousins I passbands for the previouslyunstudied open cluster NGC 5288. The sample consists of 15688 starsreaching down to V~ 20.5. The cluster appears to have a relatively smallbut conspicuous nucleus and a low-density extended coronal region. Starcounts carried out in 25 × 25 pixel2 boxes distributedthroughout the whole observed field allowed us to estimate the angularcore and corona radii as ~1.3 and 6.3arcmin, respectively. Our analysissuggests that NGC 5288 is moderately young and probably more metal-richthan the Sun. Adopting the theoretical metal content Z= 0.040, whichprovides the best global fit, we derive an age of130+40-30Myr. Simultaneously, we have obtainedcolour excesses E(B-V) = 0.75 and E(V-I) = 0.95 and an apparent distancemodulus V-MV= 14.00. The law of interstellar extinction inthe cluster direction is found to be normal. NGC 5288 is located at 2.1+/- 0.3kpc from the Sun beyond the Carina spiral feature and ~7.4kpcfrom the Galactic Centre. The cluster metallicity seems to be compatiblewith the cluster position in the Galaxy, given the recognized radialabundance gradient in the disc. For the first time, in this paper wedetermine the basic parameters for the open cluster NGC 5381, situatedin the same direction as NGC 5288. This determination was reached byusing CCD VI data published almost a decade ago by Pietrzyński etal. (1997) for NGC 5381. The properties of some open clusters alignedalong the line of sight of NGC 5288 are examined. The properties ofclusters of similar ages to NGC 5288 are also looked into. Evidence ispresented that these did not form mainly along the spiral arms butrather in the thin Galactic disc (Z~+/-100pc).
|Variable Stars in the Field of Young Open Cluster NGC 581|
We present results of the search for variable stars in the field ofyoung open cluster NGC 581. Based on 19 nights of observations, 6 newvariable stars were discovered. Two of them turned out to be eclipsingbinary systems. Another two detected variable stars are most probably ofgamma Dor type. During our observations one of the known Be starslocated in our field of view showed irregular variations of brightness,typical for this class of stars. The sixth variable star is a pulsatingred giant.
|Variable Stars in the Field of Young Open Cluster NGC 659|
We present results of the search for variable stars in young opencluster NGC 659. Based on 35 nights of observations, 7 new variablestars were discovered. Three of them are Be stars. Another three aremost probably pulsating variables of gamma Dor type. One star is adetached binary system.
|The Optical Gravitational Lensing Experiment. A CCD Search for Variable Stars in Open Clusters - NGC5999|
We report discovery of 41 variable stars in the field of the young opencluster NGC 5999. 30 stars have light curves typical for eclipsingsystems: this group contains three Algol-type and 27 WUMa type variablestars. One RR Lyr and one delta Scuti stars form a group of pulsatingvariables. Nine variable stars are of unknown type and classified asmiscellaneous. One of them is a periodic, most probablychromospherically active star. Our data are too scarce to make anyconclusion about periodicity of remaining eight variable stars.
|Optical Gravitational Lensing Experiment. A CCD Search for Variable Stars in Open Clusters -- NGC 5381|
We present results of the search for variable stars in the field of theopen cluster NGC 5381. Observations conducted from March to September1997 led to discovery of 18 new variable stars. 13 stars are eclipsingvariables; light curves of 7 of them are typical for W UMa type starsand remaining six are EA Algol-like systems. Five stars, for which wecannot estimate periods from the present data, we call tentatively longterm variables. For previously known variable QR Cen an accurate lightcurve was obtained. This star turned out to be an EA type eclipsingsystem with the period of 2.^d2903 (about two times longer than obtainedearlier).
|Catalogue of Eclipsing and Spectroscopic Binary Stars in the Regions of Open Clusters|
|Uniform survey of clusters in the southern Milky Way.|
Abstract image available at:http://adsabs.harvard.edu/abs/1975AJ.....80...11V