Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Morphology and ionization characteristics of planetary nebulae PB 1 and
  PC 19   We present results of our study of two planetary nebulae (PNe), PB1 and PC
19. We use the optical spectra of these two PNe observed at 2 m Himalayan
Chandra Telescope and also archival and literature data for the study. We use
the morphokinematic code SHAPE to construct 3D morphologies of the PNe and the
photoionization code CLOUDY to model the observed spectra. The 3D model of PB 1
consists of an elongated shell surrounded by a bipolar halo and that of PC 19
consists of an open lobed bipolar structure and a spiral filamentary pair. We
analyze the ionization structure of the PNe by deriving several plasma
parameters and by photoionization modelling. We estimate the elemental
abundances of the the elements, He, C, N, O, Ne, S, Ar, and Cl, from our
analysis. We find He, C and N abundances to be significantly higher in case of
PB 1. We estimate different physical parameters of the central stars, namely
effective temperature, luminosity and gravity, and of the nebula, namely
hydrogen density profiles, radii, etc., from photoionization modelling. We
estimate distances to the PNe as $\sim$4.3 kpc for PB 1 and as $\sim$5.6 kpc
for PC 19 by fitting the photoionization models to absolute observed fluxes.
Progenitor masses are estimated from theoretical evolutionary trajectories and
are found to be $\sim$1.67 and $\sim$2.38 $M_{\odot}$ for PB 1 and PC 19,
respectively.

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The categories of this paper are: cmp-lg
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The categories of this paper are: solv-int
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The categories of this paper are: alg-geom
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
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The categories of this paper are: gr-qc
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The categories of this paper are: bayes-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: dg-ga
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The categories of this paper are: atom-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-fin
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The categories of this paper are: funct-an