| Project/Area Number |
10640226
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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 | Nagasaki University (1999)
The University of Tokyo (1998) |
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Principal Investigator |
OSAKI Yoji Nagasaki University, Faculty of Education, Professor, 教育学部, 教授 (30011547)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 1999: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1998: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Keywords | Dwarf Novae / Cataclysmic Variables / Accretion Disks / Close Binary System / X-ray Radiation / Corona |
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| Research Abstract |
Dwarf novae are eruptive variables showing repetitive outbursts of amplitudes of 3-5 magnitude once every a few weeks to months. Dwarf novae belong to close binary systems called cataclysmic variable stars in which a Roche-lobe filling red dwarf secondary star loses mass and a white dwarf primary star accretes it via an accretion disk. It is now widely accepted that outbursts of dwarf novae may be caused by the instability in accretion disks in cataclysmic variable stars: i.e., the disk instability model which was first proposed by the present author (Osaki, 1974) in 1974. There is a rich variety in outburst light curves of various dwarf novae. A unification model for dwarf nova outbursts was proposed by the present author in 1996 within the basic framework of the disk instability model. The purpose of this research is to complete this project by investigating this model from various standpoint. Research results in this term will be summarized.
1. A model of X-ray emitting coronae aroun
… More
d a white dwarf in cataclysmic variable stars
It is known that a nearly spherical hot corona is produced around accreting white dwarfs because of thermal instability at the boundary layer if the accretion rate is below some critical value. A steady state model of this corona is constructed and the X-ray spectra are calculated as functions of the mass supply rate. It has been found that the thermal energy of the corona is transported downward by electron conduction to the denser area near the surface of the white dwarf, where it is emitted as X-ray radiation. Around 5% of the matter supplied by the disk could leave the system as stellar wind.
2. Completion of unification model for the outburst mechanism of dwarf novae
Our unification model for the outburst mechanism of dwarf novae within the disk instability paradigm was presented by myself in various international symposia and workshops. It was generally accepted warmly but several criticisms were also raised sometime and these will be useful for further development of this theory. Less
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