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arXiv · 2204.07495

Analytical Model of Disk Evaporation and State Transitions in Accreting Black Holes

Hyerin Cho·Ramesh Narayan
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Abstract

State transitions in black hole X-ray binaries are likely caused by gas evaporation from a thin accretion disk into a hot corona. We present a height-integrated version of this process which is suitable for analytical and numerical studies. With radius $r$ scaled to Schwarzschild units and coronal mass accretion rate $\dot{m}_c$ to Eddington units, the results of the model are independent of black hole mass. State transitions should thus be similar in X-ray binaries and AGN. The corona solution consists of two power-law segments separated at a break radius $r_b \sim10^3 \,(\alpha/0.3)^{-2}$, where $\alpha$ is the viscosity parameter. Gas evaporates from the disk to the corona for $r>r_b$, and condenses back for $r r_b$, and a $T\sim 5\times 10^8\,{\rm K}$ Compton-cooled corona for $r < r_b$. Two-temperature effects are ignored, but may be important at small radii.

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Hyerin Cho, Ramesh Narayan. 2022-04-15. Analytical Model of Disk Evaporation and State Transitions in Accreting Black Holes. https://doi.org/10.3847/1538-4357/ac6d5c

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