Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Soft X-ray emission from intermediate-age open clusters: IC 4651   We present the results of soft X-ray observations of the intermediate-age
open cluster IC 4651 performed with the ROSAT PSPC. We detected 25 sources. Two
are identified with a giant binary and a blue straggler respectively, both
belonging to the cluster, and two with probable main-sequence members. Two
other cases have ambiguous identification. Of the five binaries known in the
cluster, the one detected in X rays is the only one whose period is short
enough to maintain fast rotation and therefore strong stellar activity at a
high age. The detected blue straggler is probably binary, suggesting that
binarity is the key to producing a high level of X-ray emission. It is the
third blue straggler detected in X rays. The remaining sources need to be
identified through optical follow-up.

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The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
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The categories of this paper are: stat
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys
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The categories of this paper are: eess
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
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The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math