| Project/Area Number |
01540222
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Astronomy
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| Research Institution | Tokyo Metropolitan University |
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Principal Investigator |
TAKAHARA Fumio Tokyo Metropolitan University, Faculty of Science Associate Professor, 理学部, 助教授 (20154891)
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| Project Period (FY) |
1989 – 1990
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| Project Status |
Completed (Fiscal Year 1990)
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| Budget Amount *help |
¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 1990: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1989: ¥800,000 (Direct Cost: ¥800,000)
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| Keywords | Accretion Disks / Electron-Positron Pairs / X-ray Background Radiation / Mass Loss / Active Galactic Nuclei / Particle Acceleration / Shock Waves / Radio Galaxies / 活動的銀河中心核 / 相対論的プラズマ / 放射流体力学 / ジェット |
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| Research Abstract |
1. We found that for two-temperature accretion disks with electron-positron pairs, there exists a critical accretion rate above which no steady state solutions exist. This conclusion proved to hold irrespective of whether soft photons are supplied by the cyclotron higher harmonics or external thermal photons. Dynamical behavior becomes important for higher accretion rates, which is left as a future problem.
2. We investigated mass loss from accretion disks. If we give the shape of streamlines a priori, a singular point of the basic equation is shown to coincide with sonic point and the critical solution gives an appropriate solution of the wind. If we solve the shape of streamlines simultaneously under the assumption of self-similarity, singular point does not coincide with sonic point. Solutions which reach the infinity become supersonic without passing through the critical point if the density distribution in the disk is relatively flat. We started numerical study of disk winds and winds including electron-positron pairs.
3. We examined models of the X-ray background in terms of a superposition of active galactic nuclei. To resolve the problem of spectral discrepancy we must incorporate either cosmological evolution of the spectral index or spectral flattening with energy for individual sources. Either model is shown to be successful if moderate luminosity evolution is assumed.
4. We argued that shock waves in hot spots of radio galaxies can accelerate protons up to 10^<20>eV through the Fermi mechanism. We also found that for oblique shocks the efficiency of particle acceleration is enhanced up to 100 times compared with parallel shocks. Electron acceleration and its consequence on the observed properties of active galactic nuclei are interesting problems to be studied.
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