A study of the strong gravity region of the black hole in GS 1354-645

Yerong Xu; Sourabh Nampalliwar; Askar B. Abdikamalov; Dimitry Ayzenberg; Cosimo Bambi; Thomas Dauser; Javier A. Garcia; Jiachen Jiang

doi:10.3847/1538-4357/aadb9d

paper

A study of the strong gravity region of the black hole in GS 1354-645

arXiv:1807.10243 · doi:10.3847/1538-4357/aadb9d

Abstract

It is thought that the spacetime metric around astrophysical black holes is well described by the Kerr solution of Einstein's gravity. However, a robust observational evidence of the Kerr nature of these objects is still lacking. Here we fit the X-ray spectrum of the stellar-mass black hole in GS 1354-645 with a disk reflection model beyond Einstein's gravity in order test the Kerr black hole hypothesis. We consider the Johannsen metric with the deformation parameters $α_{13}$ and $α_{22}$ . The Kerr metric is recovered for $α_{13} = α_{22} = 0$ . For $α_{22} = 0$ , our measurements of the black hole spin and of the deformation parameter $α_{13}$ are $a_{*} > 0.975$ and $- 0.34 < α_{13} < 0.16$ , respectively. For $α_{13} = 0$ , we find $a_{*} > 0.975$ and $- 0.09 < α_{22} < 0.42$ . All the reported uncertainties are at 99% of confidence level for two relevant parameters.

arXiv comment6 pages, 3 figures. v2: refereed version

A study of the strong gravity region of the black hole in GS 1354-645

Abstract

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