Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Orbital solution leading to an acceptable interpretation for the
  enigmatic gamma-ray binary HESS J0632+057   High-dispersion spectroscopic monitoring of HESS J0632+057 has been carried
out over four orbital cycles in order to search for orbital modulation,
covering the entire orbital phase. We have measured radial velocity of
H$\alpha$ emission line with the method introduced by Shafter et al. (1986),
which has been successfully applied to some Be stars. The velocity is seen to
increase much earlier than expected for the orbital period of 315 days, and
much more steeply than expected at around "apastron". The period of the
H$\alpha$ modulation is found to be as $308^{+26}_{-23}$ days. We have also
analyzed Swift/XRT data from 2009 to 2015 to study the orbital modulation,
selecting the data with good statistics ($\geq$ 30 counts). With additional
two-year data to the previous works, the orbital period has been updated to
$313^{+11}_{-8}$ days, which is consistent with the previous X-ray periods and
the spectroscopic one. The past XMM-Newton and Chandra observations prefer the
period of 313 days. With the new period, assuming that H$\alpha$ velocities
accurately trace the motion of the Be star, we have derived a new set of the
orbital parameters. In the new orbit, which is less eccentric ($e \sim 0.6$),
two outbursts occur after apastron, and just after periastron. Besides, the
column density in bright phase
($4.7^{+0.9}_{-08}\times10^{21}\;\mathrm{cm^{-2}}$) is higher than in faint
phase ($2.2\pm0.5\times10^{21}\;\mathrm{cm^{-2}}$). These facts suggest that
outbursts occur when the compact object passes nearby/through the Be disk. The
mass function implies that mass of the compact object is less than 2.5
$\mathrm{M_{sun}}$ assuming that the mass of the Be star is 13.2--18.2
$\mathrm{M_{sun}}$ (Aragona at al. 2010) unless the inclination is extremely
small. The photon index indicates that the spectra becomes softer when the
system is bright. These suggest that the compact object is a pulsar.

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The categories of this paper are: atom-ph
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The categories of this paper are: stat
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The categories of this paper are: econ
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The categories of this paper are: cmp-lg
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The categories of this paper are: math
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The categories of this paper are: funct-an
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The categories of this paper are: nucl-ex
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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: solv-int
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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: ao-sci
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The categories of this paper are: hep-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg