Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Testing the No-Hair Theorem with Observations in the Electromagnetic
  Spectrum: I. Properties of a Quasi-Kerr Spacetime   According to the no-hair theorem, an astrophysical black hole is uniquely
described by only two quantities, the mass and the spin. In this series of
papers, we investigate a framework for testing the no-hair theorem with
observations of black holes in the electromagnetic spectrum. We formulate our
approach in terms of a parametric spacetime which contains a quadrupole moment
that is independent of both mass and spin. If the no-hair theorem is correct,
then any deviation of the black-hole quadrupole moment from its Kerr value has
to be zero. We analyze in detail the properties of this quasi-Kerr spacetime
that are critical to interpreting observations of black holes and demonstrate
their dependence on the spin and quadrupole moment. In particular, we show that
the location of the innermost stable circular orbit and the gravitational
lensing experienced by photons are affected significantly at even modest
deviations of the quadrupole moment from the value predicted by the no-hair
theorem. We argue that observations of black-hole images, of relativistically
broadened iron lines, as well as of thermal X-ray spectra from accreting black
holes will lead in the near future to an experimental test of the no-hair
theorem.

14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph