Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic Doppler imaging of the roAp star HD 24712   We present the first magnetic Doppler images of a rapidly oscillating Ap
(roAp) star.
  We deduce information about magnetic field geometry and abundance
distributions of a number of chemical elements on the surface of the hitherto
best studied roAp star, HD 24712, using the magnetic Doppler imaging (MDI)
code, INVERS10, which allows us to reconstruct simultaneously and consistently
the magnetic field geometry and elemental abundance distributions on a stellar
surface. For this purpose we analyse time series spectra obtained in Stokes I
and V parameters with the SOFIN polarimeter at the Nordic Optical Telescope and
recover surface abundance structures of sixteen different chemical elements,
respectively ions, including Mg, Ca, Sc, Ti, Cr, Fe, Co, Ni, Y, La, Ce, Pr, Nd,
Gd, Tb, and Dy. For the rare earth elements (REE) Pr and Nd separate maps were
obtained using lines of the first and the second ionization stage.
  We find and confirm a clear dipolar structure of the surface magnetic field
and an unexpected correlation of elemental abundances with respect to this
field: one group of elements accumulates solely where the positive magnetic
pole is visible, whereas the other group avoids this region and is enhanced
where the magnetic equatorial region dominates the visible stellar surface. We
also observe relative shifts of abundance enhancement- or depletion regions
between the various elements exhibiting otherwise similar behaviour.

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The categories of this paper are: math
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-th
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The categories of this paper are: econ
32
The categories of this paper are: atom-ph
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The categories of this paper are: physics
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
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The categories of this paper are: quant-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: eess
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The categories of this paper are: supr-con
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The categories of this paper are: q-alg