Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The complex evolution of the X-ray binary transient MAXI J1807+132 along
  the decay of its discovery outburst   MAXI J1807+132 is an X-ray transient discovered during the decay of an
outburst in 2017. We present optical and X-ray monitoring of the source over
more than 125 days, from outburst to quiescence. The outburst decay is
characterized by the presence of several re-flares with a quasi-periodic
recurrence time of $\sim 6.5$ days. We detect broad H and He emission lines
during outburst, characteristic of transient low mass X-ray binaries. These
emission lines show strong variability from epoch to epoch and, in particular,
during the early stages are found embedded into deep and very broad absorption
features. The quiescent spectrum shows H$\alpha$ in emission and no obvious
signatures of the donor star. XMM-Newton and Swift spectra can be fitted with
standard X-ray models for accreting black-holes and neutron stars, although the
obtained spectral parameters favour the latter scenario. Conversely, other
observables such as the optical/X-ray flux ratio, the likely systemic velocity
($\gamma \sim -150$ km s$^{-1}$) and the re-flares recurrence time suggest a
black hole nature. We discuss all the above possibilities with emphasis on the
strong similarities of MAXI J1807+132 with short orbital period systems.

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The categories of this paper are: math-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex
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The categories of this paper are: nucl-th
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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: nlin