Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 462, Issue 1, Pages 636-648Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stw1643
Keywords
black hole physics; gravitation; hydrodynamics; MHD; methods: numerical
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The radiative and jet efficiencies of thin magnetized accretion discs around black holes (BHs) are affected by BH spin and the presence of a magnetic field that, when strong, could lead to large deviations from Novikov-Thorne (NT) thin disc theory. To seek the maximum deviations, we perform general relativistic magnetohydrodynamic simulations of radiatively efficient thin (half-height H to radius R of H/R approximate to 0.10) discs around moderately rotating BHs with a/M = 0.5. First, our simulations, each evolved for more than 70 000 r(g)/c (gravitational radius r(g) and speed of light c), show that large-scale magnetic field readily accretes inward even through our thin disc and builds-up to the magnetically arrested disc (MAD) state. Secondly, our simulations of thin MADs show the disc achieves a radiative efficiency of eta(r) approximate to 15 per cent (after estimating photon capture), which is about twice the NT value of eta(r) similar to 8 per cent for a/M = 0.5 and gives the same luminosity as an NT disc with a/M approximate to 0.9. Compared to prior simulations with less than or similar to 10 per cent deviations, our result of an approximate to 80 per cent deviation sets a new benchmark. Building on prior work, we are now able to complete an important scaling law which suggests that observed jet quenching in the high-soft state in BH X-ray binaries is consistent with an ever-present MAD state with a weak yet sustained jet.
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