Testing General Relativity with Supermassive Black Holes Using X-Ray Reflection Spectroscopy

Abdikamalov, Askar B.; Ayzenberg, Dimitry; Bambi, Cosimo; Nampalliwar, Sourabh; Tripathi, Ashutosh; Wong, Jelen; Xu, Yerong; Yan, Jinli; Yan, Yunfeng; Yang, Yuchan

doi:10.3390/proceedings2019017002

Cited by 10 publications

(6 citation statements)

References 90 publications

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“…By calculating the transfer function for a generic stationary, axisymmetric, and asymptotically flat black hole spacetime, an extended relativistic reflection model relxill nk has been constructed (see refs. [50,51] for details on the model and [77] for a review on our results). Presently, relxill nk can work either with the Johannsen metric to measure the deformation parameters α 13 , α 22 , and 3 [50,51], or with a black hole solution from a class of conformally invariant theories of gravity with the deformation parameter L [78,79].…”

Section: X-ray Reflection Spectroscopymentioning

confidence: 99%

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

Wang

Abdikamalov

Ayzenberg

et al. 2020

J. Cosmol. Astropart. Phys.

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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, α13 = 0. Our measurement, which should be regarded as principally a proof of concept, is a * = 0.92 +0.07 −0.12 and α13 = −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.

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Section: X-ray Reflection Spectroscopymentioning

confidence: 99%

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

Wang

Abdikamalov

Ayzenberg

et al. 2020

J. Cosmol. Astropart. Phys.

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“…This expansion becomes problematic at small r for rapidly rotating BHs (e.g., near the inner edge of an accretion disk). This is exactly the regime where x-ray spectroscopy is most powerful [32,33] and typically used [34,35]. It is, therefore, essential to use a better metric to test the Kerr hypothesis, especially with xray reflection spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Testing general relativity with x-ray reflection spectroscopy: The Konoplya-Rezzolla-Zhidenko parametrization

et al. 2020

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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.

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“…X-ray reflection spectroscopy is an established technique for probing BHs in our universe. There are comprehensive reviews which describe the technique in general [58] and its implementation in the program to test alternative theories of gravity [28,59,60]. We briefly describe some important concepts in X-ray spectroscopy and the reflection component below.…”

Section: X-ray Spectroscopymentioning

confidence: 99%

Testing horizon topology with electromagnetic observations

Nampalliwar,

Suvorov,

Kokkotas

2020

Preprint

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In general relativity without a cosmological constant, a classical theorem due to Hawking states that stationary black holes must be topologically spherical. This result is one of the several ingredients that collectively imply the uniqueness of the Kerr metric. If, however, general relativity describes gravity inexactly at high energies or over cosmological scales, Hawking's result may not apply, and black holes with non-trivial topology may be, at least mathematically, permissible. While tests involving electromagnetic and gravitational-wave data have been used to place tight constraints on various theoretical departures from a Kerr description of astrophysical black holes, relatively little attention has been paid to topological alternatives. In this paper, we derive a new exact solution in an f (R) theory of gravity which admits topologically non-trivial black holes, and calculate observables like fluorescent Kα iron-line profiles and black hole images from hypothetical astrophysical systems which house these objects, to provide a theoretical basis for new tests of black hole nature. On the basis of qualitative comparisons, we show that topologically non-trivial objects would leave a strong imprint on electromagnetic observables and can be easily distinguished from general-relativistic black holes in nearly all cases.

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Testing General Relativity with Supermassive Black Holes Using X-Ray Reflection Spectroscopy

Cited by 10 publications

References 90 publications

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

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

Testing general relativity with x-ray reflection spectroscopy: The Konoplya-Rezzolla-Zhidenko parametrization

Testing horizon topology with electromagnetic observations

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