Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Variability in Proto-Planetary Nebulae: VIII. A New Sample of Southern
  Hemisphere Objects   As part of our continuing study of light variability in proto-planetary
nebulae (PPNe), we present the results from a long-term study of nine southern
hemisphere objects. We have monitored their light variations over a nine-year
interval from 2010-2018. These were supplemented by data from the ASAS-SN and
ASAS-3 surveys, leading to combined light curves from 2000 to 2020. Pulsation
periods were found in seven of the objects, although the three shortest must be
regarded as tentative. The periods range from 24 to 73 days. When compared with
the results of previous studies of the light variations in PPNe, we find that
they show the same trends of shorter period and smaller light variations with
higher temperatures. Luminosities were calculated based on the spectral energy
distributions, reddening, and Gaia distances, and these confirm the
identification of all but one as post-AGB objects. Three of the stars possess
long-period variations of 5 to 19 years. These are most likely due to the
periodic obscuration of the star by a disk, suggesting the presence of a binary
companion and a circumbinary disk.

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The categories of this paper are: comp-gas
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The categories of this paper are: hep-th
2
The categories of this paper are: math
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
22
The categories of this paper are: chao-dyn
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The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio
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The categories of this paper are: solv-int
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The categories of this paper are: nlin
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The categories of this paper are: stat