Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Enigmatic HH 255   To gain insight into the nature of the peculiar Herbig-Haro object HH 255
(also called Burnham's nebula), we use previously published observations to
derive information about the emission line fluxes as a function of position
within HH 255 and compare them with the well-studied, and relatively
well-behaved bow shock HH 1. There are some qualitative similarities in the
H$\alpha$ and [O III] 5007 lines in both objects. However, in contrast to the
expectation of the standard bow shock model, the fluxes of the [O I] 6300, [S
II] 6731, and [N II] 6583 lines are essentially constant along the axis of the
flow, while the electron density decreases, over a large distance within HH
255.
  We also explore the possibility that HH 255 represents the emission behind a
standing or quasi-stationary shock. The shock faces upwind, and we suggest,
using theoretical arguments, that it may be associated with the collimation of
the southern outflow from T Tauri. Using a simplified magnetohydrodynamic
simulation to illustrate the basic concept, we demonstrate that the existence
of such a shock at the north edge of HH 255 could indeed explain its unusual
kinematic and ionization properties. Whether or not such a shock can explain
the detailed emission line stratification remains an open question.

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The categories of this paper are: eess
3
The categories of this paper are: physics
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The categories of this paper are: nucl-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: cmp-lg
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The categories of this paper are: comp-gas
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The categories of this paper are: math
1
The categories of this paper are: cs
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The categories of this paper are: acc-phys
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The categories of this paper are: cond-mat
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The categories of this paper are: mtrl-th
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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: nlin
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The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph