Proper motions and CCD photometry of stars in the region of the open cluster NGC 6866 |
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| Authors: | V N Frolov Yu K Ananjevskaja D L Gorshanov E V Polyakov |
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| Institution: | (1) Sarhova 20, SI-1000 Ljubljana, Slovenia |
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| Abstract: | We present the results of our comprehensive study of the Galactic open star cluster NGC 6866. The positions of stars in the
investigated region have been obtained with the “Fantasy” automatic measuring machine from 10 plates of the normal astrograph
at the Pulkovo Astronomical Observatory. The size of the investigated field is 40′ × 40′, the limiting magnitude is B ∼ 16·
m
6, and the maximum epoch difference is 79 yr. For 1202 field stars, we have determined the relative proper motions with an
rms error of 2.5 mas yr−1. Out of them, 423 stars may be considered cluster members with a probability P > 70% according to the astrometric criterion. Photometric diagrams have been used as an additional criterion. We have performed
two-color BV CCD photometry of stars with the Pulkovo ZA-320M mirror astrograph. The U magnitudes from the literature have also been used to construct the two-color diagrams. A total of 267 stars have turned
out to be members of NGC 6866 according to the two criteria. We present refined physical parameters of the cluster and its
age estimate (5.6 × 108 yr). The cluster membership of red and blue giants, variable, double, and multiple stars is considered. We have found an
almost complete coincidence of the positions of one of the stars in the region (a cluster nonmember) and a soft X-ray source
in the ROSAT catalog. The “Fantasy” automatic measuring machine is described in the Appendix. |
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