| Project/Area Number |
09640323
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Astronomy
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| Research Institution | Osaka University |
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Principal Investigator |
TAKAMURA Fumio Groduate school of Science Professor, 大学院・理学研究科, 教授 (20154891)
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| Project Period (FY) |
1997 – 1998
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| Project Status |
Completed (Fiscal Year 1998)
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| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1998: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1997: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | Active Galactic Nuslei / Relativistic Jets / Electron Positron Pairs / Particle Acceleration / Accretion Disks / Gamma Ray Astronomy / Radio Galaxies / Black Holes / 高エネルギー天文学 / 衝撃波 |
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| Research Abstract |
We have made theoretical investigations on the physical properties and bulk acceleration mechanisms of relativistic jets observed in active galactic nuclei and Galactic black hole candidates.
1. For the many blazars which have been observed with ASCA, we estimated physical status of the jets utilizing the data of simultaneous multiwavelength observations and found that the energy density of relativistic electrons is much greater than that of magnetic fields. It is also argued that the jets are mainly composed of electron-positron pairs.
2. We quantitatively examined bulk acceleration of jets by radiation fields.
We assesed the degree of anisotropy of the radiation field which is required to accelerate jets up to the Lorentz factor of 10 through Thomson scattering.
We also examined acceleration by synchrotron absorption and showed that when the electron energy and magnetic field strength take most favorable values, Lorentz factor of 100 can be attained for electron-positron jets. However, resultant kinetic luminosity is limited to less than 1% of the Eddington one owing to the effects of the optical thickness.
3. We showed that hot accretion disks can produce incipient jets of electron-positron pairs. We solved electron-positron pair equilibrium in the disk taking account of the effect of pair escape and showed that major part of the dissipated power goes into thermal and kinetic energies of escaping pairs when the accretion rate is near the Eddington one. Pairs are heated by Coulomb collisions with higher temperature ions and are accelerated by their own pressure gradient. This provides a new mechanism of jet formation which is physically connected with the gravitational energy release.
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