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The magnetic nature of disk accretion onto black holes


Although disk accretion onto compact objects—white dwarfs, neutron stars and black holes—is central to much of high-energy astrophysics, the mechanisms that enable this process have remained observationally difficult to determine. Accretion disks must transfer angular momentum in order for matter to travel radially inward onto the compact object1. Internal viscosity from magnetic processes1,2,3,4 and disk winds5 can both in principle transfer angular momentum, but hitherto we lacked evidence that either occurs. Here we report that an X-ray-absorbing wind discovered in an observation of the stellar-mass black hole binary GRO J1655 - 40 (ref. 6) must be powered by a magnetic process that can also drive accretion through the disk. Detailed spectral analysis and modelling of the wind shows that it can only be powered by pressure generated by magnetic viscosity internal to the disk or magnetocentrifugal forces. This result demonstrates that disk accretion onto black holes is a fundamentally magnetic process.

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Figure 1: A small part of the disk wind spectrum observed in GRO J1655 - 40 with Chandra.
Figure 2: Comparison to the data of the best model for the disk wind in GRO J1655 - 40.


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We acknowledge conversations with N. Calvet, L. Hartmann, D. Proga and M. Rupen. We are indebted to A. Prestwich, H. Tananbaum and the Chandra staff for help in making this observation possible. We thank B. Lauritsen for editorial insights. This work was supported by NASA through the Chandra guest observer programme (J.M.M.). Author Contributions J.M.M. analysed the Chandra data and wrote most of the paper. J.R. developed the photoionization model. J.M.M., J.R., A.F. and C.R. developed the interpretation of the data. D.S., J.H., M.K. and R.W. contributed insights on X-ray binaries and/or made supporting observations with other instruments. All others discussed the work at length, and contributed to the manuscript.

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Correspondence to Jon M. Miller.

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Miller, J., Raymond, J., Fabian, A. et al. The magnetic nature of disk accretion onto black holes. Nature 441, 953–955 (2006).

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