Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Angular Momentum Exchange by Gravitational Torques and Infall in the
  Circumbinary Disk of the Protostellar System L1551 NE   We report the ALMA observation of the Class I binary protostellar system
L1551 NE in the 0.9-mm continuum, C18O (3-2), and 13CO (3-2) lines at a ~1.6
times higher resolution and a ~6 times higher sensitivity than those of our
previous SMA observations, which revealed a r ~300 AU-scale circumbinary disk
in Keplerian rotation. The 0.9-mm continuum shows two opposing U-shaped
brightenings in the circumbinary disk, and exhibits a depression between the
circumbinary disk and the circumstellar disk of the primary protostar. The
molecular lines trace non-axisymmetric deviations from Keplerian rotation in
the circumbinary disk at higher velocities relative to the systemic velocity,
where our previous SMA observations could not detect the lines. In addition, we
detect inward motion along the minor axis of the circumbinary disk. To explain
the newly-observed features, we performed a numerical simulation of gas orbits
in a Roche potential tailored to the inferred properties of L1551 NE. The
observed U-shaped dust features coincide with locations where gravitational
torques from the central binary system are predicted to impart angular momentum
to the circumbinary disk, producing shocks and hence density enhancements seen
as a pair of spiral arms. The observed inward gas motion coincides with
locations where angular momentum is predicted to be lowered by the
gravitational torques. The good agreement between our observation and model
indicates that gravitational torques from the binary stars constitute the
primary driver for exchanging angular momentum so as to permit infall through
the circumbinary disk of L1551 NE.

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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: hep-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: dg-ga
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The categories of this paper are: solv-int
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The categories of this paper are: q-alg
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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: alg-geom
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The categories of this paper are: cond-mat
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The categories of this paper are: funct-an
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ph