Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: And in the Darkness Bind Them: Equatorial Rings, B[e] Supergiants, and
  the Waists of Bipolar Nebulae   We report the discovery of two new circumstellar ring nebulae in the western
Carina Nebula. The brighter object, SBW1, resembles a lidless staring eye and
encircles a B1.5 Iab supergiant. Its size is identical to the inner ring around
SN1987A, but SBW1's low N abundance indicates that the star didn't pass through
a RSG phase. The fainter object, SBW2, is a more distorted ring, is N-rich, and
has a central star that seems to be invisible. We discuss these two new nebulae
in context with rings around SN1987A, Sher25, HD168625, RY Scuti, WeBo1, SuWt2,
and others. The ring bearers fall into two groups: Five rings surround hot
supergiants, and all except for the one known binary are carbon copies of the
ring around SN1987A. We propose a link between these rings and B[e]
supergiants, where the rings derive from the same material in an earlier B[e]
phase. The remaining four rings surround evolved intermediate-mass stars; all
members of this ring fellowship are close binaries, hinting that binary
interactions govern the forging of such rings. We estimate that there may be
several thousand more dark rings in the Galaxy, but we are scarcely aware of
their existence due to selection effects. The lower-mass objects might be the
equatorial density enhancements often invoked to bind the waists of bipolar
PNe.

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The categories of this paper are: supr-con
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The categories of this paper are: atom-ph
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
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The categories of this paper are: q-alg
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
1
The categories of this paper are: cs
12
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: hep-ex
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The categories of this paper are: mtrl-th
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: alg-geom
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The categories of this paper are: cond-mat