Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Variability in red supergiant stars: pulsations, long secondary periods
  and convection noise   We study the brightness variations of galactic red supergiant stars using
long-term visual light curves collected by the American Association of Variable
Star Observers (AAVSO) over the last century. The full sample contains 48 red
semiregular or irregular variable stars, with a mean time-span of observations
of 61 years. We determine periods and period variability from analyses of power
density spectra and time-frequency distributions. We find two significant
periods in 18 stars. Most of these periods fall into two distinct groups,
ranging from a few hundred to a few thousand days. Theoretical models imply
fundamental, first and possibly second overtone mode pulsations for the shorter
periods. Periods greater than 1000 days form a parallel period-luminosity
relation that is similar to the Long Secondary Periods of the Asymptotic Giant
Branch stars. A number of individual power spectra shows a single mode resolved
into multiple peaks under a Lorentzian envelope, which we interpret as evidence
for stochastic oscillations, presumably caused by the interplay of convection
and pulsations. We find a strong 1/f noise component in the power spectra that
is remarkably similar in almost all stars of the sample. This behaviour fits
the picture of irregular photometric variability caused by large convection
cells, analogous to the granulation background seen in the Sun.

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The categories of this paper are: nlin
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The categories of this paper are: q-fin
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The categories of this paper are: ao-sci
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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: alg-geom
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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: supr-con
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The categories of this paper are: nucl-th