Black hole continuum spectra as a test of general relativity: Quadratic gravity

Dimitry Ayzenberg, Nicolás Yunes

Research output: Contribution to journalArticlepeer-review


Observations of the continuum spectrum emitted by accretion disks around black holes allows us to infer their properties, including possibly whether black holes are described by the Kerr metric. Some modified gravity theories do not admit the Kerr metric as a solution, and thus, continuum spectrum observations could be used to constrain these theories. We here investigate whether current and next generation x-ray observations of the black hole continuum spectrum can constrain such deviations from Einstein's theory, focusing on two well-motivated modified quadratic gravity theories: dynamical Chern-Simons gravity and Einstein-dilaton-Gauss-Bonnet gravity. We do so by determining whether the non-Kerr deviations in the continuum spectrum introduced by these theories are larger than the observational error intrinsic to the observations. We find that dynamical Chern-Simons gravity cannot be constrained better than current bounds with current or next generation continuum spectrum observations. Einstein-dilaton-Gauss-Bonnet gravity, however, may be constrained better than current bounds with next generation telescopes, as long as the systematic error inherent in the accretion disk modeling is decreased below the predicted observational error.

Original languageEnglish (US)
Article number115003
JournalClassical and Quantum Gravity
Issue number11
StatePublished - May 18 2017
Externally publishedYes


  • accretion disks
  • black holes
  • continuum spectrum
  • general relativity
  • modified theories of gravity

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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