Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Modulated accretion in T Tauri star RY Tau -- stable MHD propeller or a
  planet at 0.2 AU?   Planets are thought to form at the early stage of stellar evolution when the
mass accretion is still ongoing. RY Tau is a T Tauri type star at the age of a
few Myr, with accretion disc seen at high inclination, so that line of sight
crosses both the wind and the accretion gas flows. In a long series of
spectroscopic monitoring of the star in 2013-2020, we detected variations in
H-alpha and NaI D absorptions at radial velocities of infall (accretion) and
outflow (wind) with a period of about 22 days. The absorptions in the infalling
and the outflowing gas streams vary in anti-phase: an increase of infall is
accompanied by a decrease of outflow, and vice versa. These flip-flop
oscillations retain phase over several years of observations. We suggest that
this may result from the MHD processes at the disk-magnetosphere boundary in
the propeller mode. Another possibility is that a massive planet modulates some
processes in the disc and provides the observed effects. The period, if
Keplerian, corresponds to a distance of 0.2 AU, which is close to the dust
sublimation radius in this star. The presence of the putative planet may be
confirmed by radial velocity measurements: expected amplitude is > 90 m/s if a
planet mass is > 2 Mj.

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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-bio
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: funct-an
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The categories of this paper are: hep-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: math
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The categories of this paper are: supr-con
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The categories of this paper are: math-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ph
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The categories of this paper are: dg-ga