Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Chandra observation of the globular cluster Terzan 1: the neutron-star
  X-ray transient X 1732-304 in quiescence   We present a short (~3.6 ks) Chandra/HRC-I observation of the globular
cluster Terzan 1. This cluster is known to contain the bright neutron star
low-mass X-ray binary X 1732-304 which was active during the 1980's and most of
the 1990's. But a BeppoSAX observation performed in 1999 only showed a very
weak source indicating that the source had become quiescent. During our Chandra
observation, we detect one source with a 0.5-10 keV luminosity of approximately
1 - 2 x 10^{33} erg/s (for an assumed distance of 5.2 kpc). However, its
position is not consistent with that of X 1732-304. We do not conclusively
detect X 1732-304 with a 0.5-10 keV luminosity upper limit of 0.5 - 1 x 10^{33}
erg/s. This limit is consistent with the luminosities observed for several
neutron-star X-ray transients in our Galaxy when they are quiescent, strongly
suggesting that X 1732-304 was still quiescent during our Chandra observation.
If the quiescent emission in neutron star X-ray transients is due to the
thermal emission from the neutron star, then it is expected that the quiescent
luminosity depends on the time-averaged accretion rate of the source. However,
the upper limit on the quiescent luminosity of X 1732-304, combined with its
very long accretion episode prior to the current quiescent episode, indicates
that the quiescent episodes of the source have to be longer than ~200 years.
This would be the second system after KS 1731-260 for which quiescent episodes
longer than several hundreds of years have been inferred. We discuss this
possibility and alternative quiescent models to explain our results.

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The categories of this paper are: physics
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The categories of this paper are: solv-int
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The categories of this paper are: q-bio
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The categories of this paper are: math-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: stat
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The categories of this paper are: eess
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The categories of this paper are: cs
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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
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The categories of this paper are: math
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The categories of this paper are: cond-mat
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat