Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photometric study of the variable star population in the globular
  cluster NGC 6397   We present the results of a photometric survey for variable stars in the
central region of the nearby globular cluster NGC 6397.Time series photometry
was obtained for 30 variable objects. The sample includes 12 new objects, of
which 6 show periodic lightcurves and 2 are eclipsing binaries of unknown
period. Six variables possess certain and three possess likely X-ray
counterparts detected with the Chandra observatory. Among them four are
cataclysmic variables and one is a foreground eclipsing binary. The cataclysmic
variable CV2 exhibited a likely dwarf nova type outburst in May 2003. The
cataclysmic variable CV3 was observed at 18.5<V<20.0 during 5 observing runs,
but went into a low state in May 2003 when it reached V>22. We have found that
thelight curve of the optical companion to the millisecond pulsar PSRJ1740-5340
exhibits noticeable changes of its amplitude on a time scale of a few months. A
shallow eclipse with Delta_V=0.03 mag was detected in one of the cluster
turnoff stars suggesting the presence of a large planet or brown dwarf in
orbit.

12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
11
The categories of this paper are: hep-lat
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
27
The categories of this paper are: comp-gas
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys