Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the ultra-compact nature of 4U1822-000   We report the discovery of a periodic modulation in the optical lightcurve of
the candidate ultra-compact X-ray binary 4U1822-000. Using time-resolved
optical photometry taken with the William Herschel Telescope we find evidence
for a sinusoidal modulation with a semi-amplitude of 8 percent and a period of
191 min, which is most likely close to the true orbital period of the binary.
Using the van Paradijs & McClintock relation for the absolute magnitude and the
distance modulus allowing for interstellar reddening, we estimate the distance
to 4U1822-000 to be 6.3 kpc. The long orbital period and casts severe doubts on
the ultra-compact nature of 4U1822-000.

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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
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The categories of this paper are: math-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-th
4
The categories of this paper are: cond-mat
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The categories of this paper are: chem-ph
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: q-fin
36
The categories of this paper are: cmp-lg