Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Expanding Bipolar X-ray Structure After the 2006 Eruption of RS Oph   We report on the detection and analysis of extended X-ray emission by the
{\it Chandra} X-ray Observatory stemming from the 2006 eruption of the
recurrent novae RS Oph. The extended emission was detected 1254 and 1927 days
after the start of the 2006 eruption and is consistent with a bipolar flow
oriented in the east-west direction of the sky with opening angles of
approximately $70^{\circ}$. The length of both lobes appeared to expand from
1.3 arcsec in 2009 to 2.0 arcsec in 2011, suggesting a projected expansion rate
of $1.1\pm0.1 {\rm ~mas~day}^{-1}$ and an expansion velocity of $4600\ {\rm
km~s}^{-1}\ (D/2.4\ {\rm kpc})$ in the plane of the sky. This expansion rate is
consistent with previous estimates from optical and radio observations of
material in a similar orientation. The X-ray emission does not show any
evidence of cooling between 2009 and 2011, consistent with free expansion of
the material. This discovery suggests that some mechanism collimates ejecta
away from the equatorial plane, and that after that material passes through the
red-giant wind, it expands freely into the cavity left by the 1985 eruption. We
expect similar structures to arise from latest eruption and to expand into the
cavity shaped by the 2006 eruption.

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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-ph
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The categories of this paper are: adap-org
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The categories of this paper are: comp-gas
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The categories of this paper are: chem-ph
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The categories of this paper are: nlin
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The categories of this paper are: math-ph
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The categories of this paper are: stat
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The categories of this paper are: patt-sol
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: supr-con
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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga