Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Line Emission from an Accretion Disk around a Rotating Black Hole:
  Toward a Measurement of Frame Dragging   Line emission from an accretion disk and a corotating hot spot about a
rotating black hole are considered for possible signatures of the
frame-dragging effect. We explicitly compare integrated line profiles from a
geometrically thin disk about a Schwarzschild and an extreme Kerr black hole,
and show that the line profile differences are small if the inner radius of the
disk is near or above the Schwarzschild stable-orbit limit of radius 6GM/c^2.
However, if the inner disk radius extends below this limit, as is possible in
the extreme Kerr spacetime, then differences can become significant, especially
if the disk emissivity is stronger near the inner regions. We demonstrate that
the first three moments of a line profile define a three-dimensional space in
which the presence of material at small radii becomes quantitatively evident in
broad classes of disk models. In the context of the simple, thin disk paradigm,
this moment-mapping scheme suggests formally that the iron line detected by the
Advanced Satellite for Cosmology and Astrophysics mission from MCG-6-30-15
(Tanaka et al. 1995) is 3 times more likely to originate from a disk about a
rotating black hole than from a Schwarzschild system. A statistically
significant detection of black hole rotation in this way may be achieved after
only modest improvements in the quality of data. We also consider light curves
and frequency shifts in line emission as a function of time for corotating hot
spots in extreme Kerr and Schwarzschild geometries. Both the frequency-shift
profile and the light curve from a hot spot are valuable measures of orbital
parameters and might possibly be used to detect frame dragging even at radii
approaching 6GM/c^2 if the inclination angle of the orbital plane is large.

1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
11
The categories of this paper are: hep-lat
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
4
The categories of this paper are: cond-mat
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn