Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic field geometry and chemical abundance distribution of the
  He-strong star CPD -57 3509   The magnetic field of CPD -57 3509 was recently detected in the framework of
the BOB (B fields in OB stars) collaboration. We acquired low-resolution
spectropolarimetric observations of CPD -57 3509 with FORS2 and high-resolution
UVES observations randomly distributed over a few months to search for
periodicity, to study the magnetic field geometry, and to determine the surface
distribution of silicon and helium. We also obtained supplementary photometric
observations at a timeline similar to the spectroscopic and spectropolarimetric
observations. A period of 6.36d was detected in the measurements of the mean
longitudinal magnetic field. A sinusoidal fit to our measurements allowed us to
constrain the magnetic field geometry and estimate the dipole strength in the
range of 3.9-4.5kG. Our application of the Doppler imaging technique revealed
the presence of He I spots located around the magnetic poles, with a strong
concentration at the positive pole and a weaker one around the negative pole.
In contrast, high concentration Si III spots are located close to the magnetic
equator. Further, our analysis of the spectral variability of CPD -57 3509 on
short time scales indicates distinct changes in shape and position of line
profiles possibly caused by the presence of beta Cep-like pulsations. A small
periodic variability in line with the changes of the magnetic field strength is
clearly seen in the photometric data.

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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: cond-mat
27
The categories of this paper are: comp-gas
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The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
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The categories of this paper are: nucl-ex
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The categories of this paper are: math
19
The categories of this paper are: eess
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The categories of this paper are: cmp-lg
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The categories of this paper are: chem-ph
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The categories of this paper are: stat
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The categories of this paper are: gr-qc
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The categories of this paper are: adap-org
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The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci