Large Scale Jets in Microquasars     

Stéphane Corbel 《Astrophysics and Space Science》2005,300(1-3):275-281

Relativistic jets are now believed to be a fairly ubiquitous property of accreting compact objects, and are intimately coupled with the accretion history. Associated with rapid changes in the accretion states of the binary systems, ejections of relativistic plasma can be observed at radio frequencies on timescale of weeks before becoming undetectable. However, recent observations point to long-term effects of these ejecta on the interstellar medium with the formation of large-scale relativistic jets around binary systems. In this paper, we review the observations of these large-scale structures in microquasars, highlighting their contributions at high energies.  相似文献   

The betatron effect in collapsing magnetic traps     

B. V. Somov  S. A. Bogachev 《Astronomy Letters》2003,29(9):621-628

We consider the question of how the betatron effect affects the particle acceleration in a magnetic trap with a rapidly decreasing length. We show that the additional increase in energy caused by the betatron acceleration as the trap contracts is exactly offset by the decrease in the time of particle confinement in the trap, because the loss cone becomes larger during the contraction. As a result, the particle energy at the time of escape from the trap remains the same as that in a collapsing trap without contraction. We estimate the Alfvén-pumping efficiency in a collapsing trap in connection with the problem of particle acceleration in solar flares. The additional energy acquired by particles from magnetic-field oscillations is shown to be negligible. We discuss the possible observational manifestations of the betatron effect in solar flares.  相似文献   

The masses of central supermassive black holes and the variability time-scales in gamma-ray loud blazars     

E. W. Liang  H. T. Liu 《Monthly notices of the Royal Astronomical Society》2003,340(2):632-638

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Gamma-ray emission from an accretion flow around a Kerr black hole     

Kazutaka Oka  Tadahiro Manmoto 《Monthly notices of the Royal Astronomical Society》2003,340(2):543-550

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Erratum: Hydromagnetic stability of a slim disc in a stationary geometry     

Rafael Angel Araya-Góchez 《Monthly notices of the Royal Astronomical Society》2003,339(3):912-912

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Ultraluminous X-ray source populations in normal galaxies: a preliminary survey with Chandra     

P. J. Humphrey  G. Fabbiano  M. Elvis  M. J. Church  M. Ba&#;uci&#;ska-Church 《Monthly notices of the Royal Astronomical Society》2003,344(1):134-148

We present results of a Chandra survey of the ultraluminous X-ray sources (ULX) in 13 normal galaxies, in which we combine source detection with X-ray flux measurement. 22 ULX were detected, i.e. with   L _x > 1 × 10³⁹ erg s⁻¹ ( L ₁₀)  and 39 other sources were detected with   L _x > 5 × 10³⁸ erg s⁻¹ ( L ₅)  . We also use radial intensity profiles to remove extended sources from the sample. The majority of sources are not extended, which for a typical distance constrains the emission region size to less than 50 pc. X-ray colour–colour diagrams and spectral fitting results were examined for indicators of the ULX nature. In the case of the brighter sources, spectral fitting generally requires two-component models. In only a few cases do colour–colour diagrams or spectral fitting provide evidence of a black hole nature. We find no evidence of a correlation with stellar mass, however, there is a strong correlation with star formation as indicated by the 60-μm flux as found in previous studies.  相似文献   

低维动态黑洞的熵     

LI Chen  SHEN Yougen   《中国科学院上海天文台年刊》2003,(1)

运用在砖墙模型方法的基础上发展起来的薄膜模型计算了 1 1维和 2 1维动态时空中的黑洞的熵。结果表明在低维动态时空中 ,黑洞熵仍满足Bekenstein -Hawking熵与面积的关系  相似文献   

Sgr A*的结构和变化:银河中心的超大质量黑洞     

赵军辉 《天文研究与技术》2003,(1):41-54

银河中心为我们提供了一个唯一的天体物理实验室来用以研究各式各样的天体物理过程。在文中 ,我们总结和归纳了关于SgrA 观测的最新结果 ,主要涉及源的结构和在流量密度方面的变化。SgrA 现象代表着在低光度活动星系核中围绕一个超大质量黑洞的低辐射率的吸积盘外流的典型例子。从SgrA 观测得到的许多天体物理中悬而未决的问题对现存的天体物理理论是一个挑战。对SgrA 的最新理论模型也作了综述。  相似文献   

Self-similar structure of magnetized radiation-dominated accretion discs     

M. Shadmehri  F. Khajenabi 《Monthly notices of the Royal Astronomical Society》2005,361(2):719-724

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Extreme gravitational lensing near rotating black holes     

Kris Beckwith  Chris Done 《Monthly notices of the Royal Astronomical Society》2005,359(4):1217-1228

We describe a new approach to calculating photon trajectories and gravitational lensing effects in the strong gravitational field of the Kerr black hole. These techniques are applied to explore both the imaging and spectral properties of photons emitted from an accretion disc, which perform multiple orbits of the central mass before escaping to infinity. Viewed at large inclinations, these higher-order photons contribute ∼20 per cent of the total luminosity of the system for a Schwarzschild hole, while for an extreme Kerr black hole this fraction rises to ∼60 per cent. In more realistic models, these photons will be reabsorbed by the disc at large distances from the hole, but this returning radiation could provide a physical mechanism to resolve the discrepancy between the predicted and observed optical/ultraviolet colours in active galactic nuclei. Conversely, at low inclinations, higher-order images reintercept the disc plane close to the black hole, so need not be absorbed by the disc if this is within the plunging region. These photons form a bright ring carrying approximately 10 per cent of the total disc luminosity for a Schwarzschild black hole. The spatial separation between the inner edge of the disc and the ring is similar to the size of the event horizon. This is resolvable for supermassive black holes with proposed X-ray interferometery missions such as the Microarcsecond X-ray Imaging Mission (MAXIM), and so has the potential to provide an observational test of strong field gravity.  相似文献