Constraint on the quadrupole moment of super-massive black hole candidates from the estimate of the mean radiative efficiency of AGN

Abstract

The super-massive objects at the center of many galaxies are commonly thought to be black holes. In 4-dimensional general relativity, a black hole is completely specified by its mass $M$ and by its spin angular momentum $J$. All the higher multipole moments of the gravitational field depend in a very specific way on these two parameters. For instance, the mass quadrupole moment is $Q=-J^2/M$. If we can estimate $M$, $J$, and $Q$ for the super-massive objects in galactic nuclei, we over-constrain the theory and we can test the black hole hypothesis. While there are many works studying how this can be done with future observations, in this paper a constraint on the quadrupole moment of these objects is obtained by using the current estimate of the mean radiative efficiency of AGN. In terms of the anomalous quadrupole moment $q$, the bound is $-2.01<q<0.14$.

4 pages, 2 figures. v2: refereed version

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• The non-integrability of the Zipoy-Voorhees metric
• A Symmetric Integrator for non-integrable Hamiltonian Relativistic Systems
• Testing the existence of regions of stable orbits at small radii around black hole candidates
• Periodic Orbits and Escapes in Dynamical Systems
• Energy Extraction via Magnetic Reconnection in the Ergosphere of a rotating non-Kerr Black Hole
• Radiation drag in the field of a non-spherical source