| Project/Area Number |
63540197
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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 | Osaka University |
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Principal Investigator |
MIYAMOTO Sigenori Osaka University, Department of Physics, Professor, 理学部, 教授 (70013638)
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| Co-Investigator(Kenkyū-buntansha) |
KITAMOTO Shunji Osaka University, Department of Physics, Research associate., 理学部, 助手 (70177872)
TSUNEMI Hiroshi Osaka University, Department of Physics, Research associate., 理学部, 助手 (90116062)
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| Project Period (FY) |
1988 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1989: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1988: ¥700,000 (Direct Cost: ¥700,000)
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| Keywords | X-ray star / X-ray nova / Compton scattering / Black hole / neutron star / X-ray radiation / Phase lag / Time lag / X線星 / X線放射メカニズム / 逆コンプトン散乱 / 宇宙X線塵散乱 / ブラックホール / X線星モニター観測 / X線星スピン周期変化 |
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| Research Abstract |
Time variation of X-rays from binary X-ray stars are observed with the all sky monitor, (ASM) and the large area counters (LAC) onboard GINGA. With ASM we found more than 13 so-called X-ray novas. Among these, there are GS2000+25 and GS2023+338, which seem to be black hole candidates because of their time variations and energy spectra of X-rays. We also studied the X-ray time variations of Cygnus X-1 and GX339-4, which were also black hole candidates.
We discovered GS2023+25 on 26th April 1989. Its whole behavior from the appearance to the disappearance was very similar to the black hole candidate X- ray star AO620-00.
GS2023+338 was discovered on 21st May 1989. This source showed very large, short and long term time variations up to the factor of about 500 before 1st of June. After this time, this source showed rapid time variations which was very similar to those of Cygnus X-1 in its low state. The power density spectrum and the lag time structure of its time variations were similar to those of Cygnus X-1.
Cygnus X-1 was observed with LAC, and we found the structure of the time lag of the time variations can not be explained by the Compton scattering model, which had been assumed to explain the energy spectrum of this source. We also found there were two characteristic time constants of about 0.2 sec and 0.7 sec, with which we could reproduce the power density spectrum and phase lag structure of X-rays from this source.
We found there existed very high state in GX339-4 from the observation with ASM. We also observed this source with LAC and found the phase lag structure could be explained by the existence of the Compton scattering cloud of the size of about 2 10^9cm. Based on this fact we proposed a jet model which can explain the energy spectrum and the phase lag structure of this source.
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