Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Bubble Nebula NGC 7635 -- testing the wind-blown bubble theory   We present a multiwavelength study of the iconic Bubble Nebula (NGC 7635) and
its ionising star BD$+$60$^{\circ}$2522. We obtained XMM-Newton EPIC X-ray
observations to search for extended X-ray emission as in other similar
wind-blown bubbles around massive stars. We also obtained San Pedro M\'{a}rtir
spectroscopic observations with the Manchester Echelle Spectrometer to study
the dynamics of the Bubble Nebula. Although our EPIC observations are deep, we
do not detect extended X-ray emission from this wind-blown bubble. On the other
hand, BD$+$60$^{\circ}$2522 is a bright X-ray source similar to other O stars.
We used the stellar atmosphere code PoWR to characterise BD$+$60$^{\circ}$2522
and found that this star is a young O-type star with stellar wind capable of
producing a wind-blown bubble that in principle could be filled with hot gas.
We discussed our findings in line with recent numerical simulations proposing
that the Bubble Nebula has been formed as the result of the fast motion of
BD$+$60$^{\circ}$2522 through the medium. Our kinematic study shows that the
Bubble Nebula is composed by a series of nested shells, some showing
blister-like structures, but with little signatures of hydrodynamical
instabilities that would mix the material producing diffuse X-ray emission as
seen in other wind-blown bubbles. Its morphology seems to be merely the result
of projection effects of these different shells.

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The categories of this paper are: ao-sci
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: supr-con
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The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: stat
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The categories of this paper are: physics
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The categories of this paper are: gr-qc
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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: math
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The categories of this paper are: math-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: mtrl-th
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The categories of this paper are: atom-ph