Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Period variation in BW Vulpeculae redux   For the past 25 years, BW Vulpeculae has been the topic of period analyses
centered on a secular period change with a periodic variation superposed,
presumed to be due to light time effects in a binary system. According to this
paradigm, one would expect what seems like a period increase of about 0.5 s
during or soon after the year 2001. I have continued photometric monitoring
through the year 2012, adding 35 new timings of maximum and minimum light. This
expected change in period did not occur, which rules out that interpretation of
the period variation. As of 2012, the observed timings are about two hours
early compared to those predicted by the quadratic ephemeris, but are very
close to those predicted by the linear ephemeris. In fact, the period has
remained constant for the last 32 years, indicating that the previous epochs of
constant period are almost certainly the correct interpretation, though the
cause of the period changes is still not clear. Continued photometric
monitoring of BW Vul leads to the conclusion that the period changes are
abrupt, followed by epochs of constant period lasting between 12 and at least
32 years.

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The categories of this paper are: cond-mat
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The categories of this paper are: solv-int
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The categories of this paper are: q-alg
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The categories of this paper are: econ
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The categories of this paper are: nucl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: eess
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ph
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: alg-geom