| Project/Area Number |
61540183
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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 | Kyoto University |
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Principal Investigator |
MATSUDA Takuya Faculty of Engineering, Kyoto University Associate Professor Kyoto University, 工学部, 助教授 (20026206)
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| Co-Investigator(Kenkyū-buntansha) |
TAKEDA hidenori Faculty of engineering, Kyoto University Research Associate, 工学部, 助手 (80026343)
桜井 健郎 京都大学, 工学部, 教授 (30025837)
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| Project Period (FY) |
1986 – 1987
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| Project Status |
Completed (Fiscal Year 1987)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1987: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1986: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Keywords | Accretion / X-Ray Stars / Spinup / Spindown / Galaxy / Spiral Arm / Numerical Simulation / アクリーション円盤 / X線パルサー / 近接連星系 |
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| Research Abstract |
Numerical simulations on an accretion flow and a related problem were performed. There are two types of accretion flow in a close binary system depending on the mangitude of the angular momentum of the accreting gas: a Roche lobe overflow and a wind-fed accretion. In the former case we have pointed out the existence of spiral shock waves on an accretion disc. In the present work our numerical results show good agreement with the anlytic solution obtained by Spruit. According to his theory there is a close relation between the pitch angle of the spiral shocks and the specific heat ratio. The smaller the specific heat ratio, the smaller the pitch angle. We have shown that accretion can occur even without a viscosity in some cases.
Relating to the problem of the accretion, we have investigated the problem of spiral arm formation in a disc galaxy. In our view, the cause of spiral arms are a deviatin of gravitational force from the exact axisymmetry. In the accretin disc very similar phenomenon occurs due to the tidal force.
We have also investigated the wind-fed accretion and the angular momentum accretion on to a compact object in a close binary system. We found that the flow is unsteady and the sign of the angular momentum of the accreting gas changes randomly with time. Although this is an unexpected result, Taam & Fryxcell in USA recently confirmed our results by their extensive numerical simulations. We have very new picture on the spin-up/down phenomena of a compact object. Our results can explain observations well.
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