期刊
PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN
卷 61, 期 3, 页码 L7-L11出版社
OXFORD UNIV PRESS
DOI: 10.1093/pasj/61.3.L7
关键词
accretion, accretion disks; black hole physics; ISM: jets and outflows; magnetohydrodynamics: MHD; radiative transfer
资金
- Ministry of Education, Culture, Sports, Science, and Technology (MEXT) [20740115, 19340044]
- special postdoctoral researchers program of RIKEN (KO)
- JSPS [14740132]
- Grants-in-Aid for Scientific Research [14740132, 20740115, 21244013] Funding Source: KAKEN
Black-hole accretion systems are known to possess several distinct modes (or spectral states), such as low/hard state and high/soft state. Since the dynamics of the corresponding flows is distinct, theoretical models were separately considered for each state. We here propose a unified model based on our new, global, two-dimensional radiation-magnetohydrodynamic simulations. By controlling a density normalization we could for the first time reproduce three distinct modes of accretion flow and outflow with one numerical code. When the density is large (model A), a geometrically thick, very luminous disk forms, in which photon trapping takes place. When the density is moderate (model B), the accreting gas can effectively be cooled by emitting radiation, thus generating a thin disk, i.e., a soft-state disk. When the density is too low for radiative cooling to be important (model C), a disk becomes hot, thick, and faint; i.e., a hard-state disk. The magnetic energy is amplified within the disk up to about twice, 30%, and 20% of the gas energy in models A, B, and C, respectively. Notably, the disk outflows with helical magnetic fields, which are driven either by radiation-pressure force or magnetic-pressure force, are ubiquitous in any accretion modes. Finally, our simulations are consistent with the phenomenological alpha-viscosity prescription; that is, the disk viscosity is proportional to the pressure.
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