Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Variable stars in the field of the old open cluster Melotte 66   We report the results of photometric monitoring of the Melotte 66 field in
BVI filters. Ten variables were identified with nine being new discoveries. The
sample includes eight eclipsing binaries of which four are W UMa type stars,
one star is a candidate blue straggler. All four contact binaries are likely
members of the cluster based on their estimated distances. Ten blue stars with
U-B<-0.3 were detected inside a 14.8 x 22.8 arcmin^2 field centred on the
cluster. Time series photometry for 7 of them showed no evidence for any
variability. The brightest object in the sample of blue stars is a promising
candidate for a hot subdwarf belonging to the cluster. We show that the
anomalously wide main sequence of the cluster, reported in some earlier
studies, results from a combination of two effects: variable reddening occuring
across the cluster field and the presence of a rich population of binary stars
in the cluster itself. The density profile of the cluster field is derived and
the total number of member stars with 16<V<21 or 2.8<M_{V}<7.8 is estimated
conservatively at about 1100.

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The categories of this paper are: comp-gas
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The categories of this paper are: q-alg
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The categories of this paper are: physics
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The categories of this paper are: dg-ga
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The categories of this paper are: cmp-lg
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The categories of this paper are: acc-phys
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The categories of this paper are: chao-dyn
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The categories of this paper are: supr-con
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The categories of this paper are: econ
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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
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The categories of this paper are: bayes-an