Testing general relativity with x-ray reflection spectroscopy: The Konoplya-Rezzolla-Zhidenko parametrization
X-ray reflection spectroscopy is a promising technique for testing general relativity in the strong-field regime as it can be used to test the Kerr black hole hypothesis. In this context, the parametrically deformed black hole metrics proposed by Konoplya, Rezzolla, and Zhidenko [Phys. Rev. D 93, 064015 (2016)] form an important class of non-Kerr black holes. We implement this class of black hole metrics in relxill_nk, which is a framework we have developed for testing for non-Kerr black holes using x-ray reflection spectroscopy. We perform a qualitative analysis of the effect of the leading order strong-field deformation parameters on typical observables like the innermost stable circular orbits and the reflection spectra. We also present the first x-ray constraints on some of the deformation parameters of this metric, using Suzaku data from the supermassive black hole in Ark 564, and compare them with those obtained (or expected) from other observational techniques like gravitational waves and black hole imaging.
Additional Information© 2020 American Physical Society. (Received 4 April 2019; revised 14 October 2020; accepted 2 December 2020; published 28 December 2020) We thank Alejandro Cardenas-Avendano for pointing out the issue with matching the metric to the Kerr solution, and Roman Konoplya and Alexander Zhidenko for providing the correct metric components. We also thank the anonymous referee whose valuable feedback helped us improve the paper. S. N. acknowledges support from the Excellence Initiative at Eberhard-Karls Universität Tübingen. S. N. and J. A. G. also acknowledge support from the Alexander von Humboldt Foundation. A. B. A. acknowledges the support from the Shanghai Government Scholarship (SGS). A. T. acknowledges support from the China Scholarship Council (CSC), Grant No. 2016GXZR89. The authors acknowledge support by the High Performance and Cloud Computing Group at the Zentrum für Datenverarbeitung of the University of Tübingen, the state of Baden-Württemberg through bwHPC and the German Research Foundation (DFG) through Grant No. INST 37/935-1 FUGG. This work was supported by the National Natural Science Foundation of China (NSFC), Grant No. U1531117, and Fudan University, Grant No. IDH1512060.
Published - PhysRevD.102.124071.pdf
Submitted - 1903.12119.pdf