Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: B fields in OB stars (BOB): low-resolution FORS2 spectropolarimetry of
  the first sample of 50 massive stars   Within the context of the collaboration "B fields in OB stars (BOB)", we used
the FORS2 low-resolution spectropolarimeter to search for a magnetic field in
50 massive stars, including two reference magnetic massive stars. Because of
the many controversies of magnetic field detections obtained with the FORS
instruments, we derived the magnetic field values with two completely
independent reduction and analysis pipelines. We compare and discuss the
results obtained from the two pipelines. We obtained a general good agreement,
indicating that most of the discrepancies on magnetic field detections reported
in the literature are caused by the interpretation of the significance of the
results (i.e., 3-4 sigma detections considered as genuine, or not), instead of
by significant differences in the derived magnetic field values. By combining
our results with past FORS1 measurements of HD46328, we improve the estimate of
the stellar rotation period, obtaining P = 2.17950+/-0.00009 days. For
HD125823, our FORS2 measurements do not fit the available magnetic field model,
based on magnetic field values obtained 30 years ago. We repeatedly detect a
magnetic field for the O9.7V star HD54879, the HD164492C massive binary, and
the He-rich star CPD -57 3509. We obtain a magnetic field detection rate of
6+/-4%, while by considering only the apparently slow rotators we derive a
detection rate of 8+/-5%, both comparable with what was previously reported by
other similar surveys. We are left with the intriguing result that, although
the large majority of magnetic massive stars is rotating slowly, our detection
rate is not a strong function of the stellar rotational velocity.

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The categories of this paper are: nlin
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The categories of this paper are: econ
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The categories of this paper are: plasm-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: physics
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: cmp-lg
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat