Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Flaring X-ray Source with an Halpha-bright Counterpart toward the SMC   We report the discovery of a flaring X-ray source with an optical counterpart
with Halpha emission and red-excess, in the direction of the SMC. A 100 ksec
X-ray observation with Chandra detected a flare lasting 6 ksec in the source
CXO J005428.9-723107. The X-ray spectrum during the flare was consistent with a
thermal plasma of temperature kT=2.5 keV. In quiescence following the flare the
spectrum was softer (kT= 0.4 keV). Timing analysis did not reveal any
significant periodicities or QPOs. Optical images taken with the Magellan-Baade
6.5m telescope show a single star in the (0.9") error circle. This star has
apparent magnitude V=19.17, exhibits enhanced Halpha emission (Halpha - r =
-0.88), and has a large proper motion. Alternative explanations are explored,
leading to identification as a relatively nearby (Galactic) coronally active
star of the BY Draconis class.

36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int