Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Orbital Period of the Ultraluminous X-ray Source in M82   The ultraluminous x-ray source (ULX) in the galaxy M82 has been identified as
a possible intermediate-mass black hole. We have found that the x-ray flux from
M82 is modulated with a peak-to-peak amplitude corresponding to an isotropic
luminosity of 2.4x10^40 erg/s in M82 and a period of 62.0 +/- 2.5 days, which
we interpret as the orbital period of the ULX binary. This orbital period
implies that the mass-donor star must be a giant or supergiant. Large
mass-transfer rates, sufficient to fuel the ULX, are expected for a giant-phase
mass donor in an x-ray binary. The giant phase has a short lifetime, indicating
that we see the ULX in M82 in a brief and unusual period of its evolution.

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The categories of this paper are: patt-sol
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th
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The categories of this paper are: supr-con
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ph
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The categories of this paper are: stat
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The categories of this paper are: nlin
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: math-ph
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The categories of this paper are: math
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The categories of this paper are: dg-ga
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The categories of this paper are: atom-ph
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The categories of this paper are: cmp-lg