Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Galactic planetary nebulae with Wolf-Rayet nuclei. II. A consistent
  observational data set   We present high resolution spectrophotometric data for 34 galactic planetary
nebulae with [WC] nuclei (WRPNe).The sample includes PNe with early and late
[WC] stars and some WELS. Physical conditions and chemical abundances have been
derived and expansion velocities were estimated for most objects of the sample.
A statistical study was developed to find fundamental relationships between the
nebular and central star parameters.We found evidence for a strong unexpected
electron temperature gradient in WRPNe which is related to nebular excitation.
Abundance ratios indicate that there seems to be no preferential stellar mass
for the WR phenomenon to occur in the nucleus of a planetary nebula. The PNe M
1-25 and M 1-32 were found to have very small Ne/O ratios.Our data confirm the
trend of the electron density decreasing with decreasing spectral type, which
was interpreted as evidence that [WC] stars evolve from late to early [WC]
types. On the other hand, the expansion velocities do not show the increase
with decreasing spectral type, that one might expect in such a scenario. Two
objects with very late [WC] central stars, K 2-16 and PM 1-188, do not follow
the general density sequence, being of very low density for their spectral
types. We suggest that the stars either underwent a late helium flash (the
``born again'' scenario) or that they have had a particularly slow evolution
from the AGB. The 6 WELS of our sample follow the same density vs. [WC]-type
relation as the bona fide WRPNe, but they tend to have smaller expansion
velocities. The comparison between the WRPNe in the Magellanic Clouds and in
the Galaxy indicates that metallicity affects the [WR] phenomenon in central
stars of planetary nebulae.

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The categories of this paper are: eess
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
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The categories of this paper are: cmp-lg
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The categories of this paper are: quant-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: math
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The categories of this paper are: econ
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The categories of this paper are: nlin
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The categories of this paper are: q-alg
4
The categories of this paper are: cond-mat
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The categories of this paper are: patt-sol
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-ex
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The categories of this paper are: dg-ga