Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Localization of the X-ray Source in the Globular Cluster G1 with Chandra   We report the most accurate X-ray position of the X-ray source in the giant
globular cluster G1 in M31 by using the Chandra X-ray Observatory, Hubble Space
Telescope (HST), and Canada-France-Hawaii Telescope (CFHT). G1 is clearly
detected with Chandra and by cross-registering with HST and CFHT images, we
derive a 1-sigma error radius of 0.15 arcsec, significantly smaller than the
previous measurement by XMM-Newton. We conclude that the X-ray emission of G1
is likely to come from within the core radius of the cluster. We have
considered a number of possibilities for the origin of the X-ray emission but
can rule all but two scenarios out: it could be due to either accretion onto a
central intermediate-mass black hole (IMBH), or an ordinary low-mass X-ray
binary (LMXB). Based on the X-ray luminosity and the Bondi accretion rate, an
IMBH accreting from the cluster gas seems unlikely and we suggest that the
X-rays are due to accretion from a companion. Alternatively, the probability
that a 1.5 solar masses cluster LMXB lies within the 95 per cent X-ray error
circle is about 0.7. Therefore we cannot rule out a single LMXB as the origin
of the X-ray emission. While we cannot distinguish between different models
with current observations, future high-resolution and high-sensitivity radio
imaging observations will reveal whether there is an IMBH at the centre of G1.

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The categories of this paper are: q-bio
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The categories of this paper are: patt-sol
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-ex
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The categories of this paper are: physics
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The categories of this paper are: supr-con
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The categories of this paper are: eess
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The categories of this paper are: chem-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: math
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The categories of this paper are: q-alg
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The categories of this paper are: econ