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# Magnetic origin of black hole winds across the mass scale

## Abstract

Invariably, black hole accretion disks seem to produce plasma outflows that result in blue-shifted absorption features in their spectra1. The X-ray absorption-line properties of these outflows are diverse, ranging in velocity from non-relativistic2 (~300 km s–1) to sub-relativistic3 (~0.1c, where c is the speed of light) and a similarly broad range in the ionization states of the wind plasma2,4. We report here that semi-analytical, self-similar magnetohydrodynamic wind models that have successfully accounted for the X-ray absorber properties of supermassive black holes5,6 also offer a good fit to the high-resolution X-ray spectrum of the accreting stellar-mass black hole GRO J1655–40. This provides an explicit theoretical argument of their magnetohydrodynamic origin (aligned with earlier observational claims)7 and supports the notion of a universal magnetic structure of the observed winds across all known black hole sizes.

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## Acknowledgements

We thank T. Kallman for providing us with the Chandra/HETG data for GRO J1655–40. K.F., D.K. and C.S. acknowledge support by a NASA/ADP grant. E.B. received funding from the European Unions Horizon 2020 research and innovation programm under the Marie Sklodowska-Curie grant agreement no. 655324. and from the I-CORE program of the Planning and Budgeting Committee (grant number 1937/12). Support for this work was in part provided by NASA through Chandra Award Number AR6-17013A issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060.

## Author information

Authors

### Contributions

K.F. led the overall model development and data fitting procedures. D.K., C.S, E.B. and F.T. each contributed to the validation, interpretation and presentation of the final results. The baseline wind model was originally formulated by I.C. In particular, D.K. provided insights connecting our results to the broader picture of accretion-induced outflows in astrophysical environments and E.B. provided technical advice on the details of atomic physics crucial to the X-ray spectroscopic analyses in this work. All authors contributed to writing the manuscript and preparing the figures and tables.

### Corresponding author

Correspondence to Keigo Fukumura.

## Ethics declarations

### Competing interests

The authors declare no competing financial interests.

## Supplementary information

### Supplementary Information

Supplementary Figures 1–4 and Supplementary Tables 1–2. (PDF 541 kb)

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Reprints and Permissions

Fukumura, K., Kazanas, D., Shrader, C. et al. Magnetic origin of black hole winds across the mass scale. Nat Astron 1, 0062 (2017). https://doi.org/10.1038/s41550-017-0062

• Accepted:

• Published:

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