Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Does the Iron K$_{\alpha}$ Line of Active Galactic Nuclei Arise from the
  Cerenkov Line-like Radiation?   When thermal relativistic electrons with isotropic distribution of velocities
move in a gas region, or impinge upon the surface of a cloud that consists of a
dense gas or doped dusts, the Cerenkov effect produces peculiar atomic or ionic
emission lines -- the Cerenkov line-like radiation. This newly recognized
emission mechanism may find wide applications in high-energy astrophysics. In
this paper, we tentatively adopt this new line emission mechanism to discuss
the origin of iron K$_{\alpha}$ feature of AGNs. Motivation of this research is
to attempt a solution to a problem encountered by the ``disk-fluorescence
line'' model, i.e. the lack of temporal response of the observed iron
K$_{\alpha}$ line flux to the changes of the X-ray continuum flux. If the
Cerenkov line emission is indeed responsible significantly for the iron
K$_{\alpha}$ feature, the conventional scenario around the central supermassive
black holes of AGNs would need to be modified to accommodate more energetic,
more violent and much denser environments than previously thought.

0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
3
The categories of this paper are: physics
2
The categories of this paper are: math
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
11
The categories of this paper are: hep-lat