Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chemical spots on the surface of the strongly magnetic Herbig Ae star HD
  101412   Due to the knowledge of the rotation period and the presence of a rather
strong surface magnetic field, the sharp-lined young Herbig Ae star HD 101412
with a rotation period of 42 d has become one of the most well-studied targets
among the Herbig Ae stars. High-resolution HARPS polarimetric spectra of HD
101412 were recently obtained on seven different epochs. Our study of the
spectral variability over the part of the rotation cycle covered by HARPS
observations reveals that the line profiles of the elements Mg, Si, Ca, Ti, Cr,
Mn, Fe, and Sr are clearly variable while He exhibits variability that is
opposite to the behaviour of the other elements studied. Since classical Ap
stars usually show a relationship between the magnetic field geometry and the
distribution of element spots, we used in our magnetic field measurements
different line samples belonging to the three elements with the most numerous
spectral lines, Ti, Cr, and Fe. Over the time interval covered by the available
spectra, the longitudinal magnetic field changes sign from negative to positive
polarity. The distribution of field values obtained using Ti, Cr, and Fe lines
is, however, completely different compared to the magnetic field values
determined in previous low-resolution FORS 2 measurements, where hydrogen
Balmer lines are the main contributors to the magnetic field measurements,
indicating the presence of concentration of the studied iron-peak elements in
the region of the magnetic equator. Further, we discuss the potential role of
contamination by the surrounding warm circumstellar matter in the appearance of
Zeeman features obtained using Ti lines.

1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
25
The categories of this paper are: patt-sol