Measuring Black Hole Spin Using X-Ray Reflection Spectroscopy

By C. Reynolds. 2013

389 citations recorded by the source corpus.

I review the current status of X-ray reflection (a.k.a. broad iron line) based black hole spin measurements. This is a powerful technique that allows us to measure robust black hole spins across the mass range, from the stellar-mass black holes in X-ray binaries to the supermassive black holes in active galactic nuclei. After describing the basic assumptions of this approach, I lay out the detailed methodology focusing on “best practices” that have been found necessary to obtain robust results. Reflecting my own biases, this review is slanted towards a discussion of supermassive black hole (SMBH) spin in active galactic nuclei (AGN). Pulling together all of the available XMM-Newton and Suzaku results from the literature that satisfy objective quality control criteria, it is clear that a large fraction of SMBHs are rapidly-spinning, although there are tentative hints of a more slowly spinning population at high (M>5×107 M⊙) and low (M<2×106 M⊙) mass. I also engage in a brief review of the spins of stellar-mass black holes in X-ray binaries. In general, reflection-based and continuum-fitting based spin measures are in agreement, although there remain two objects (GRO J1655–40 and 4U 1543–475) for which that is not true. I end this review by discussing the exciting frontier of relativistic reverberation, particularly the discovery of broad iron line reverberation in XMM-Newton data for the Seyfert galaxies NGC 4151, NGC 7314 and MCG–5-23-16. As well as confirming the basic paradigm of relativistic disk reflection, this detection of reverberation demonstrates that future large-area X-ray observatories such as LOFT will make tremendous progress in studies of strong gravity using relativistic reverberation in AGN.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/dd8c96e7d7a7a49c28d72be384e68cc70a5ac6ae

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Citations in the corpus

Normalizing a Relativistic Model of X-ray Reflection: The Definition of the Reflection Fraction and its Implementation in relxill (2016, background): “This is a plausible observational selection effect that helps to explain the observed prevalence of high-spin black holes (see, e.g., Reynolds 2014; Middleton 2015), but we also note that this effect can be partly explained by a larger radiative efficiency of the rapidly rotating black holes (see…”
The Masses and Spins of Neutron Stars and Stellar-Mass Black Holes (2014, background): “Spin measurements are even more sparse among quasars, but early measurements again point to high spin values and sustained disk accretion as an important mode of mass growth [340, 341, 342].”
Spinning black hole binary dynamics, scattering amplitudes, and effective field theory (2020, background): “As highlighted by the recent detection of black hole spin during inspiral phase [48], such effects are of considerable importance in light of astrophysical evidence that black holes can have a variety of intrinsic angular momenta, including close to maximally-allowed values [49].”
The spin of the second-born black hole in coalescing binary black holes (2018, background): “Many BHs exist in binary systems with non-degenerate companion stars, for example, X-ray binaries, which makes it possible to obtain the BH’s properties indirectly (McClintock 2006; McClintock et al. 2014; Reynolds 2014; Casares & Jonker 2014; Miller & Miller 2015).”
The Kerr metric (2014, background): “) About two dozen spins have been estimated [156, 160], many suggesting that rapidly spinning massive Kerr black holes do actually exist.”
Testing black hole candidates with electromagnetic radiation (2015, methodology): “…geometry around BH candidates with X-ray measurements are the study of the thermal spectrum of thin disks (continuum-fitting method) (Li et al., 2005; McClintock et al., 2014; Zhang et al., 1997) and the analysis of the iron Kα line (Brenneman & Reynolds, 2006; Fabian et al., 1989; Reynolds, 2014).”
BAT AGN Spectroscopic Survey. V. X-Ray Properties of the Swift/BAT 70-month AGN Catalog (2017, background): “…is likely to be due to relativistic reflection from the innermost region of the accretion flow (e.g., Fabian et al. 2000; Brenneman & Reynolds 2009; Reynolds 2014), although at least for some objects it might be due to the distortion of the X-ray continuum created by highly-ionized absorbing…”