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Published October 1, 2018 | Submitted + Published
Journal Article Open

A Study of the Strong Gravity Region of the Black Hole in GS 1354–645


It is thought that the spacetime metric around astrophysical black holes is well described by the Kerr solution of Einstein's gravity. However, 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.

Additional Information

© 2018. The American Astronomical Society. Received 2018 July 27; revised 2018 August 14; accepted 2018 August 18; published 2018 October 1. This work was supported by the National Natural Science Foundation of China (NSFC), grant No. U1531117, and Fudan University, grant No. IDH1512060. S.N. acknowledges support from the Excellence Initiative at Eberhard-Karls Universität Tübingen. A.B.A. also acknowledges the support from the Shanghai Government Scholarship (SGS). C.B. and J.A.G. also acknowledge support from the Alexander von Humboldt Foundation. J.J. is supported by the Cambridge Trust and the Chinese Scholarship Council Joint Scholarship Program (201604100032).

Attached Files

Published - Xu_2018_ApJ_865_134.pdf

Submitted - 1807.10243


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August 22, 2023
October 18, 2023