High energy radiation from jets and accretion disks near rotating black holes

O'Riordan, Michael; Pe'er, Asaf; McKinney, Jonathan C.

High energy radiation from jets and accretion disks near rotating black holes

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Published Version

Date

2017-01

Authors

O'Riordan, Michael

Pe'er, Asaf

McKinney, Jonathan C.

Publisher

American Institute of Physics Publishing

Published Version

10.1063/1.4968946

Abstract

We model the low/hard state in X-ray binaries as a magnetically arrested accretion flow, and calculate the resulting radiation using a general-relativistic radiative transport code. Firstly, we investigate the origin of the high-energy emission. We find the following indications of a significant jet contribution at high energies: (i) a pronounced γ-ray peak at ∼ 1023 Hz, (ii) a break in the optical/UV band where the spectrum changes from disk to jet dominated, and (iii) a low-frequency synchrotron peak ≲ 1014 Hz implies that a significant fraction of any observed X-ray and γ-ray emission originates in the jet. Secondly, we investigate the effects of black hole spin on the high-energy emission. We find that the X-ray and γ-ray power depend strongly on spin and inclination angle. Surprisingly, this dependence is not a result of the Blandford-Znajek mechanism, but instead can be understood as a redshift effect. For rapidly rotating black holes, observers with large inclinations see deeper into the hot, dense, highly-magnetized inner regions of the accretion flow. Since the lower frequency emission originates at larger radii, it is not significantly affected by the spin. Therefore, the ratio of the X-ray to near-infrared power is an observational probe of black hole spin.

Keywords

Spin , Black hole , Radiation , Emission

Citation

O’Riordan, M., Pe’er, A. and McKinney, J.C. (2017) ‘High energy radiation from jets and accretion disks near rotating black holes’, AIP Conference Proceedings 1792, 040042, (6pp). doi: 10.1063/1.4968946