Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sharp-Lined and Slowly Rotating Ap Stars   One of the most intriguing properties of the Ap (and Bp) stars is their slow
rotation, compared to the superficially normal main-sequence stars in the same
temperature range. In recent years, it has emerged that several percent of the
Ap stars have rotation periods exceeding one year, and that the longest
rotation periods reach several centuries. Perhaps even more puzzling is the
spread of the rotation periods of the Ap stars, as some of them are as short as
0.5 d. Thus, the rotation periods of these stars span 5 to 6 orders of
magnitude, with no evidence for evolution besides conservation of the angular
momentum during their main-sequence lifetime. Explaining how period
differentiation over such a wide range is achieved in stars that are
essentially at the same evolutionary stage represents a major challenge.
  Consideration of the extremely slowly rotating Ap stars is of particular
importance for the understanding of the origin and the evolution of the
rotational properties of Ap stars as a class. We review recent progress in the
knowledge of the periods and magnetic fields of the sharpest-lined and most
slowly rotating Ap stars, and discuss the prospects and concerns for future
progress in their study.

24
The categories of this paper are: dg-ga
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
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The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
15
The categories of this paper are: nucl-ex
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an