期刊
CLASSICAL AND QUANTUM GRAVITY
卷 30, 期 24, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0264-9381/30/24/244004
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- Institute of Astronomy at the National Central University (Jhongli, Taiwan)
- NASA [NNX10AE41G, NNX10AR31G, NNX12AE13G]
- NASA [NNX10AR31G, 125408, NNX12AE13G, 53392, 135457, NNX10AE41G] Funding Source: Federal RePORTER
Black hole spin is a quantity of great interest to both physicists and astrophysicists. We review the current status of spin measurements in supermassive black holes (SMBH). To date, every robust SMBH spin measurement uses x-ray reflection spectroscopy, so we focus almost exclusively on this technique as applied to moderately-luminous active galactic nuclei (AGN). After describing the foundations and uncertainties of the method, we summarize the current status of the field. At the time of writing, observations by XMM-Newton, Suzaku and NuSTAR have given robust spin constraints on 22 SMBHs. We find a significant number of rapidly rotating SMBHs (with dimensionless spin parameters a > 0.9) although, especially at the higher masses (M > 4 x 10(7)M(circle dot)), there are also some SMBHs with intermediate spin parameters. This may be giving us our first hint at a mass-dependent spin distribution which would, in turn, provide interesting constraints on models for SMBH growth. We also discuss the recent discovery of relativistic x-ray reverberation which we can use to 'echo map' the innermost regions of the accretion disc. The ultimate development of these reverberation techniques, when applied to data from future high-throughput x-ray observatories such as LOFT, ATHENA+, and AXSIO, will permit the measurement of black hole spin by a characterization of strong-field Shapiro delays. We conclude with a brief discussion of other electromagnetic methods that have been attempted or are being developed to constrain SMBH spin.
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