Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Explaining the asymmetric line profile in Cepheus X-4 with spectral
  variation across pulse phase   The high mass X-ray binary Cep X-4, during its 2014 outburst, showed evidence
for an asymmetric cyclotron line in its hard X-ray spectrum. The 2014 spectrum
provides one of the clearest cases of an asymmetric line profile among all
studied sources with Cyclotron Resonance Scattering Features (CRSF). We present
a phase-resolved analysis of NuSTAR and Suzaku data taken at the peak and
during the decline phases of this outburst. We find that the pulse-phased
resolved spectra are well-fit by a single, symmetric cyclotron feature. The fit
parameters vary strongly with pulse phase: most notably the central energy and
depth of the cyclotron feature, the slope of the power-law component, and the
absorbing column density. We synthesise a phase averaged spectrum using the
best-fit parameters for these individual pulse phases, and find that this
combined model spectrum has a similar asymmetry in the cyclotron features as
discovered in phase-averaged data. We conclude that the pulse phase resolved
analysis with simple symmetric line profiles when combined can explain the
asymmetry detected in the phase-averaged data.

9
The categories of this paper are: nlin
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th