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|New catalogue of blue stragglers in open clusters|
We present a catalogue of blue-straggler candidates in galactic openclusters. It is based on the inspection of the colour-magnitude diagramsof the clusters, and it updates and supersedesthe first version(Ahumada & Lapasset 1995). A new bibliographical search was made foreach cluster, and the resulting information is organised into twotables. Some methodological aspects have been revised, in particularthose concerning the delimitation of the area in the diagrams where thestragglers are selected.A total of 1887 blue-straggler candidates have been found in 427 openclusters of all ages, doubling the original number. The catalogued starsare classified into two categories mainly according to membershipinformation.The whole catalogue (Tables 8, 9, notes, and references) is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (188.8.131.52) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/463/789
|The young open cluster NGC 2129|
The first charge-coupled device UBV(RI)C photometric study inthe area of the doubtful open cluster NGC 2129 is presented. Photometryof a field offset 15 arcmin northwards is also provided, to probe theGalactic disc population towards the cluster. Using star counts, propermotions from the UCAC2 catalogue, colour-magnitude and colour-colourdiagrams, we demonstrate that NGC 2129 is a young open cluster. Thecluster radius is 2.5 arcmin, and across this region we find evidence ofsignificant differential reddening, although the reddening law seems tobe normal towards its direction. Updated estimates of the clusterfundamental parameters are provided. The mean reddening is found to beE(B-V) = 0.80 +/- 0.08 and the distance modulus is (m-M)0=11.70 +/- 0.30. Hence, NGC 2129 is located at 2.2 +/- 0.2 kpc from theSun inside the Local spiral arm. The age derived from 37 photometricallyselected members is estimated to be approximately 10 Myr. These starsare used to provide new estimates of the cluster absolute proper-motioncomponents.
|A photometric study of the young open cluster NGC 1220|
We present UBV CCD observations obtained in the field of the northernopen cluster NGC 1220, for which little information is available. Weprovide also BV CCD photometry of a field 5' northward of NGC1220 to take into account field star contamination. We argue that NGC1220 is a young compact open cluster, for which we estimate a coreradius in the range 1.5-2.0 arcmin. We identify 26 likely candidatemembers with spectral type earlier than A5, down to Vo=15.00mag on the basis of the position in the two-colour Diagram and in theColour Magnitude Diagrams (CMDs). By analyzing the distribution of thesestars in the colour-colour and CMDs, we find that NGC 1220 has areddening E(B-V)=0.70+/-0.15 mag, is placed 1800+/-200 pc distant fromthe Sun, and has an age of about 60 Myrs. The cluster turns out to belocated about 120 pc above the Galactic plane, relatively high withrespect to its age. Based on observations carried out at Observatorio deS. Pedro Martir, UNAM, Mexico. Photometry is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(184.108.40.206) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/391/179
|Interstellar Extinction Along the Camelopardalis and Perseus Border|
Interstellar extinction in a ~ 100 sq. degree area at theCamelopardalis and Perseus border is investigated. The study is basedon the results of photoelectric photometry of 455 stars in theseven-color Vilnius photometric system published earlier. The nearest100 stars with Hipparcos parallaxes show that the extinction starts togrow at a distance of 110--150 pc. At a distance of 1 kpc theextinction A_V is within 1.2 and 2.4 mag. At larger distances theextinction determination is affected by the limiting magnitude effect.At distances >1.5 kpc a number of O--B stars with the extinctionsbetween 2 and 4 mag are found.
|Development of the Galactic disk: A search for the oldest open clusters|
In an extensive charge coupled devices (CCD) photometric survey ofpotential old open clusters, we have identified a number of systems thatare indeed old; some of them are among the oldest of the open clusters.Using our versions of two well-known morphological age indices, onebased on the luminosity difference between the main sequence turnoff andthe horizontal branch and the other on the color difference between theturnoff and the giant branch, we have ranked the open clusters inapproximate order of age. Our data together with previously publishedphotometry of other old open clusters, yields a catalogue of 72 clustersof the age of Hyades or older with 19 of the clusters as old or olderthan M67 (about 5 Gyr). Among the oldest open clusters are Be 17, Cr261, NGC 6791, Be 54, and AM 2. Be 17 and another old cluster, Lynga 7,are possibly as old as the youngest globulars. The data also suggestthat the formation rate of open clusters may have been higher early inthe history of the disk than at intermediate times since numerousclusters have survived from that time.
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