Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Episodic Mass Loss from the Hydrogen-Deficient Central Star of the
  Planetary Nebula Longmore 4   A spectacular transient mass-loss episode from the extremely hot,
hydrogen-deficient central star of the planetary nebula (PN) Longmore 4 was
discovered in 1992 by Werner et al. During that event, the star temporarily
changed from its normal PG 1159 spectrum to that of an emission-line
low-luminosity early-type Wolf-Rayet [WCE] star. After a few days, Lo 4
reverted to its normal, predominantly absorption-line PG 1159 type. To
determine whether such events recur, and if so how often, I monitored the
optical spectrum of Lo 4 from early 2003 to early 2012. Out of 81 spectra taken
at random dates, four of them revealed mass-loss outbursts similar to that seen
in 1992. This indicates that the episodes recur approximately every 100 days
(if the recurrence rate has been approximately constant and the duration of a
typical episode is ~5 days), and that the star is in a high-mass-loss state
about 5% of the time. Since the enhanced stellar wind is hydrogen-deficient, it
arises from the photosphere and is unlikely to be related to phenomena such as
a binary or planetary companion or infalling dust. I speculate on plausible
mechanisms for these unique outbursts, including the possibility that they are
related to the non-radial GW Vir-type pulsations exhibited by Lo 4. The central
star of the PN NGC 246 has stellar parameters similar to those of Lo 4, and it
is also a GW Vir-type pulsator with similar pulsation periods. I obtained 167
spectra of NGC 246 between 2003 and 2011, but no mass ejections were found.

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The categories of this paper are: nucl-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: acc-phys
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The categories of this paper are: nlin
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The categories of this paper are: supr-con
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The categories of this paper are: math-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: chem-ph
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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: cond-mat
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-th
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex