Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The impact of rotation on the line profiles of Wolf-Rayet stars   Massive Wolf-Rayet stars are recognized today to be in a very common, but
short, evolutionary phase of massive stars. While our understanding of
Wolf-Rayet stars has increased dramatically over the past decades, it remains
unclear whether rapid rotators are among them. There are various indications
that rapidly rotating Wolf-Rayet stars should exist. Unfortunately, due to
their expanding atmospheres, rotational velocities of Wolf-Rayet stars are very
difficult to measure. However, recently observed spectra of several Wolf-Rayet
stars reveal peculiarly broad and round emission lines. Could these spectra
imply rapid rotation?
  In this work, we model the effects of rotation on the atmospheres of
Wolf-Rayet stars. We further investigate whether the peculiar spectra of five
Wolf-Rayet stars may be explained with the help of stellar rotation, infer
appropriate rotation parameters, and discuss the implications of our results.
We make use of the Potsdam Wolf-Rayet (PoWR) non-LTE model atmosphere code.
Since the observed spectra of Wolf-Rayet stars are mainly formed in their
expanding atmospheres, rotation must be accounted for with a 3D integration
scheme of the formal integral. For this purpose, we assume a rotational
velocity field consisting of an inner co-rotating domain and an outer domain,
where the angular momentum is conserved. We find that rotation can reproduce
the unique spectra analyzed here. However, the inferred rotational velocities
at the stellar surface are large (~200 km/s), and the inferred co-rotation
radii (~10 stellar radii) suggest the existence of very strong photospheric
magnetic fields (~20 kG).

27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
4
The categories of this paper are: cond-mat
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
3
The categories of this paper are: physics
0
The categories of this paper are: hep-ph
26
The categories of this paper are: bayes-an