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Testing the Kerr metric using X-ray reflection spectroscopy: spectral analysis of GX 339-4

Wang-Ji, Jingyi and Abdikamalov, Askar B. and Ayzenberg, Dimitry and Bambi, Cosimo and Dauser, Thomas and García, Javier A. and Nampalliwar, Sourabh and Steiner, James F. (2018) Testing the Kerr metric using X-ray reflection spectroscopy: spectral analysis of GX 339-4. . (Submitted)

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Reflection features commonly observed in the X-ray spectrum of black holes can be used to probe the strong gravity region around these objects. In this paper, we extend previous work in the literature and we employ the first full emission model for relativistic reflection in non-Kerr spacetime to test the Kerr black hole hypothesis. We analyze a composite spectrum from the detector RXTE PCU-2 of the stellar-mass black hole GX 339-4 in its brightest hard state. With an unprecedented sensitivity of ∼0.1% and 40 million counts to capture the faint features in the reflection spectrum, we demonstrate that it is possible with existing data and an adequate model to place constraints on the black hole spin a∗ and the Johannsen deformation parameter α13. For a Kerr black hole of general relativity, α_(13) = 0. Our measurement, which should be regarded as principally a proof of concept, is a∗ = 0.92^(+0.07)_(−0.12) and α_(13) = −0.76^(+0.78)_(−0.60) with a 90% confidence level and is consistent with the hypothesis that the compact object in GX 339-4 is a Kerr black hole.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Bambi, Cosimo0000-0002-3180-9502
Dauser, Thomas0000-0003-4583-9048
García, Javier A.0000-0003-3828-2448
Steiner, James F.0000-0002-5872-6061
Additional Information:J.W. thanks the Cahill Center for Astronomy and Astrophysics at Caltech for support and hospitality during her visit. This work was supported by the National Natural Science Foundation of China (NSFC), Grant No. U1531117, and Fudan University, Grant No. IDH1512060. 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. S.N. acknowledges support from the Excellence Initiative at Eberhard-Karls Universität Tübingen. J.F.S. has been supported by NASA Einstein Fellowship Grant PF5-160144.
Funding AgencyGrant Number
National Natural Science Foundation of ChinaU1531117
Fudan UniversityIDH1512060
Shanghai Government ScholarshipUNSPECIFIED
Alexander von Humboldt FoundationUNSPECIFIED
Eberhard-Karls Universität TübingenUNSPECIFIED
NASA Einstein FellowshipPF5-160144
Record Number:CaltechAUTHORS:20181009-091424392
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90182
Deposited By: Tony Diaz
Deposited On:09 Oct 2018 17:09
Last Modified:17 Dec 2019 21:48

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