paper

Quasi-normal modes of rotating black holes in Einstein-dilaton Gauss-Bonnet gravity: the second order in rotation

arXiv:2207.11267 · doi:10.1103/PhysRevD.106.104009

Abstract

One of the most promising strategies to test gravity in the strong-field, large curvature regime is gravitational spectroscopy: the measurement of black hole quasi-normal modes from the ringdown signal emitted in the aftermath of a compact binary coalescence, searching for deviations from the predictions of general relativity. This strategy is only effective if we know how quasi-normal modes of black holes are affected by modifications of general relativity; and if we know this for rotating black holes, since binary coalescences typically lead to black holes with spins . In this article, we compute for the first time the gravitational quasi-normal modes of rotating black holes up to second order in the spin in a modified gravity theory. We consider Einstein-dilaton Gauss-Bonnet gravity, one of the simplest theories which modifies the large-curvature regime of gravity and which can be tested with black hole observations. To enhance the domain of validity of the spin expansion, we perform a Padé resummation of the quasi-normal modes. We find that when the second order in spin is not included, the effect of gravity modifications may be seriously underestimated. A comparison with the general relativistic case suggests that this approach should be accurate up to spins ; therefore, our results can be used in the data analysis of ringdown signals.

19 pages, 6 figures, 5 tables. Minor changes to match the version published in Phys. Rev. D. arXiv admin note: text overlap with arXiv:2103.09870

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