Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nova-Like Cataclysmic Variable TT Ari: QPO Behaviour Coming Back From
  Positive Superhumps   We study the variability of the nova-like cataclysmic variable TT Ari, on
time-scales of between minutes and months. The observations in the filter R
were obtained at the 40-cm telescope of the Chungbuk National University
(Korea). TT Ari was in the "negative superhump" state after its return from the
"positive superhump" state, which lasted 8 years. The ephemeris for 12 best
pronounced minima is $T_{min}=BJD 2453747.0700(47)+0.132322(53)E.$ where
numbers in digits are errors in units of the last digit. The phases of minima
may reach 0.2, indicating non-eclipse nature of these minima. The
quasi-periodic oscillations (QPO) are present with a mean "period" of 21.6 min
and mean semi-amplitude of 36 mmag. This value is consistent with the range
15-25 minutes reported for previous "negative superhump" states and does not
support the hypothesis of secular decrease of the QPO period.
  Either the period, or the semi-amplitude show significant night-to-night
variations. According to the position at the two-parameter diagrams, the
interval of observations was splitted into 5 parts, showing different
characteristics which are discussed in this paper. The system is an excellent
laboratory to study processes resulting in variations at time-scales from
seconds to decades and needs further monitoring at various states of activity.

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The categories of this paper are: econ
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The categories of this paper are: alg-geom
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The categories of this paper are: math-ph
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The categories of this paper are: hep-th
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
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The categories of this paper are: math
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The categories of this paper are: ao-sci
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-lat
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The categories of this paper are: nlin
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The categories of this paper are: adap-org
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-ph