http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
X-ray Observations of Black-Hole Binaries
Tadayasu Dotani 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.6
The current status of X-ray observations of black-hole binaries is reviewed. A black-hole binary (BHB) is a close binary system consisting of a black hole (candidate) and a mass-donating normal star. It may be the best target to study the accretion phenomena, such as the structure of the accretion flow and the emission mechanisms of the X/γ-ray radiation because of the simplicity of the system. In spite of the simplicity, a BHB shows a variety of phenomena: a typical example may be the occasional state transition, i.e., qualitative changes in the spectral and timing behaviors. We summarize the observational results of BHBs, emphasizing those obtained by the Suzaku satellite and discuss their implications for our understanding of the accretion flow. The current status of X-ray observations of black-hole binaries is reviewed. A black-hole binary (BHB) is a close binary system consisting of a black hole (candidate) and a mass-donating normal star. It may be the best target to study the accretion phenomena, such as the structure of the accretion flow and the emission mechanisms of the X/γ-ray radiation because of the simplicity of the system. In spite of the simplicity, a BHB shows a variety of phenomena: a typical example may be the occasional state transition, i.e., qualitative changes in the spectral and timing behaviors. We summarize the observational results of BHBs, emphasizing those obtained by the Suzaku satellite and discuss their implications for our understanding of the accretion flow.
X-RAY ARCHIVAL DATA ANALYSIS OF TIME VARIABILITIES IN SEYFERT GALAXY MCG-2-58-22
CHOI CHUL-SUNG,DOTANI TADAYASU,YI INSU,FLETCHER ANDRE,KIM CHULHEE The Korean Astronomical Society 2001 Journal of The Korean Astronomical Society Vol.34 No.3
We report results from an analysis of the X-ray archival data on MCG-2-58-22 obtained with Ginga, ROSAT and ASCA. By analyzing both short- and long-term light curves, we find clear time variations, ranging widely from, $\~10^3$ s to more than several years, in the X-ray energy range 0.1 - 10 keV. In addition, a flare is detected in 1991, overlaid on a gradual, secular flux decrease from 1979 to 1993; this flare has a time scale of about 1 year, and the X-ray flux increased by at least a factor of 3. The implications of these observational results are discussed in terms of accretion flow dynamics near a supermassive black hole.
LONG-TERM X-RAY VARIABILITIES OF THE SEYFERT GALAXY MCG-2-58-22 : SECULAR FLUX DECREASE AND FLARES
CHOI CHUL-SUNG,DOTANI TADAYASU,CHANG HEON- YOUNG,YI INSU The Korean Astronomical Society 2002 Journal of The Korean Astronomical Society Vol.35 No.1
We have studied the long-term X-ray light curve (2-10 keV) of the luminous Seyfert 1 galaxy MCG-2-58-22 by compiling data, from various X-ray satellites, which together cover more than 20 years. We have found two distinct types of time variations in the light curve. One is a gradual and secular decrease of the X-ray flux, and the other is the episodic increase of X-ray flux (or flare) by a factor of 2-4 compared with the level expected from the secular variation. We detected 3 such flares in total; a representative duration for the flares is $\~$2 years, with intervening quiescent intervals lasting $\~$6-8 years. We discuss a few possible origins for these variabilities. Though a standard disk instability theory may explain the displayed time variability in the X-ray light curve, the subsequent accretions of stellar debris, from a tidal disruption event caused by a supermassive black hole in MCG-2-58-22, cannot be ruled out as an alternative explanation.
A SPECTROSCOPIC STUDY OF THE SEYFERT GALAXY MCG-2-58-22
Choi, Chul-Sung,Dotani, Tadayasu,Chang, Heon-Young The Korean Astronomical Society 2005 Journal of The Korean Astronomical Society Vol.38 No.3
We present analysis results of the energy spectra of MCG-2-58-22 associated with occasional flares which appear in a long-term X-ray light curve. We measure an intrinsic power-law slope of this object to be ${\Gamma}=1.74{\pm}0.02$ in the energy range of ${\sim}1-5keV$ and find that this slope is little affected by flares. We confirm that there exists a broad excess emission above 5 keV to the power-law continuum. The excess emission is less variable compared with a flux variation of flare and tends to be relatively weak during flares. A soft X-ray spectrum is also found to change, implying the presence of a variable soft component. We discuss the implications of these spectral variations.