Simulations of ultrarelativistic magnetodynamic jets from gamma-ray burst engines     

Alexander Tchekhovskoy  Jonathan C. McKinney †  Ramesh Narayan 《Monthly notices of the Royal Astronomical Society》2008,388(2):551-572

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On an excitation mechanism for trapped inertial waves in discs around black holes     

Bárbara T. Ferreira  Gordon I. Ogilvie 《Monthly notices of the Royal Astronomical Society》2008,386(4):2297-2310

According to one model, high-frequency quasi-periodic oscillations (QPOs) can be identified with inertial waves, trapped in the inner regions of accretion discs around black holes due to relativistic effects. In order to be detected, their amplitudes need to reach large enough values via some excitation mechanism. We work out in detail a non-linear coupling mechanism suggested by Kato, in which a global warping or eccentricity of the disc has a fundamental role. These large-scale deformations combine with trapped modes to generate 'intermediate' waves of negative energy that are damped as they approach either their corotation resonance or the inner edge of the disc, resulting in amplification of the trapped waves. We determine the growth rates of the inertial modes, as well as their dependence on the spin of the black hole and the properties of the disc. Our results indicate that this coupling mechanism can provide an efficient excitation of trapped inertial waves, provided the global deformations reach the inner part of the disc with non-negligible amplitude.  相似文献   

Weighing the black holes in ultraluminous X-ray sources through timing     

P. Casella  G. Ponti  A. Patruno  T. Belloni  G. Miniutti  L. Zampieri 《Monthly notices of the Royal Astronomical Society》2008,387(4):1707-1711

We describe a new method to estimate the mass of black holes in Ultraluminous X-ray Sources (ULXs). The method is based on the recently discovered 'variability plane', populated by Galactic stellar-mass black-hole candidates (BHCs) and supermassive active galactic nuclei (AGNs), in the parameter space defined by the black-hole mass, accretion rate and characteristic frequency. We apply this method to the two ULXs from which low-frequency quasi-periodic oscillations have been discovered, M82 X-1 and NGC 5408 X-1. For both sources we obtain a black-hole mass in the range  100–1300 M_⊙  , thus providing evidence for these two sources to host an intermediate-mass black hole.  相似文献   

Broad reprocessed Balmer emission from warped accretion discs     

Sheng-Miao Wu  Ting-Gui Wang  Xiao-Bo Dong 《Monthly notices of the Royal Astronomical Society》2008,389(1):213-222

Double-peaked broad emission lines in active galactic nuclei are generally considered to be formed in an accretion disc. In this paper, we compute the profiles of reprocessing emission lines from a relativistic, warped accretion disc around a black hole in order to explore the possibility that certain asymmetries in the double-peaked emission-line profile which cannot be explained by a circular Keplerian disc may be induced by disc warping. The disc warping also provides a solution for the energy budget in the emission-line region because it increases the solid angle of the outer disc portion subtended to the inner portion of the disc. We adopted a parametrized disc geometry and a central point-like source of ionizing radiation to capture the main characteristics of the emission-line profile from such discs. We find that the ratio between the blue and red peaks of the line profiles becoming less than unity can be naturally predicted by a twisted warped disc, and a third peak can be produced in some cases. We show that disc warping can reproduce the main features of multipeaked line profiles of four active galactic nuclei from the Sloan Digital Sky Survey.  相似文献   

A synthesis model for AGN evolution: supermassive black holes growth and feedback modes     

Andrea Merloni  Sebastian Heinz 《Monthly notices of the Royal Astronomical Society》2008,388(3):1011-1030

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Characteristics of the Radiation from Blazars     

Yong-gang Zheng  Wei-guo Yang  Hao-jing Zhang  Xiong Zhang   《Chinese Astronomy and Astrophysics》2008,32(2):140-150

We have collected short-timescale variability data of 47 blazars, estimated the masses of their central black holes and the sizes of their radiation regions at different wavebands, and made a statistical analysis on the calculated results. It is found that the central black hole mass of blazars falls in the range 10⁷M to 10¹⁰M, and that the BL Lac objects and the flat-spectrum radio quasars have very different central black hole masses (the latter being generally greater), while they have very similar sizes of radiation regions in the infrared and γ-ray wavebands. Also, using the collected bolometric luminosity data, we have analyzed the relationship between the bolometric luminosity of blazars and their short-timescale variability, and it is concluded that the radiations from the radio-selected BL Lac objects (RBLs) and flat-spectrum radio quasars (FSRQs) are strongly beam-confined, while the effect of relativistic beaming is relatively small for the X-ray-selected BL Lac objects (XBLs).  相似文献   

Black hole at the center of the globular cluster M15: Estimation of the mass and specific angular momentum     

A. A. Kiselev  Yu. N. Gnedin  N. A. Shakht  E. A. Grosheva  M. Yu. Piotrovich  T. M. Natsvlishvili 《Astronomy Letters》2008,34(8):529-536

Using the technique of determining the sum of the masses of double stars, we have estimated the mass of the central object in the globular cluster M15. The radial velocities of stars at distances up to 1″ from the cluster center have been used. The parameters of circular orbits and the space velocities of 11 selected field stars relative to the cluster center have been determined from the calculated velocity dispersions with respect to the mean radial velocity. Based on the mean space velocity V, 14 km s^?1, and using the energy integral, we have estimated the mass of the central object to be within the range (1?9) × 10³ M _⊙. We have estimated the kinetic power of the outflow of matter from the region surrounding the black hole in M15 and the specific angular momentum of the black hole.  相似文献   

黔北黑色岩系的铂族元素地球化学特征及成因探讨   总被引：19，自引：3，他引：16       下载免费PDF全文

易发成  杨剑  侯兰杰  汪建中 《地质科学》2004,39(3):367-374

采用中子活化分析方法,系统测定了黔北黑色岩系的铂族元素含量。结果表明:金属富集层是铂族元素富集的首选层位。根据铂族元素丰度、元素相关性、特征参数值和元素配分模式,认为铂族元素并非来源于地外物质,而是海底含矿热卤水沿深大断裂而来。铂族元素的异常富集是海底热卤水与正常海水共同作用的结果。  相似文献   

岩石风化与岩石化学成分的变化研究   总被引：10，自引：0，他引：10  

巫锡勇  罗健  魏有仪 《地质与勘探》2004,40(4):85-88

研究岩石风化过程中岩石化学成分的变化规律,对于进一步研究岩石的风化机理以及岩石的物理力学性质变化过程有着十分重要的意义.本文通过对湘西地区陡山沱组黑色岩石不同风化程度的化学成分分析研究表明,岩石中的化学成分将随风化的进行而不断发生变化,在一定程度上反映了陡山沱组黑色岩石风化过程中其化学成分的变化趋势.  相似文献   

黔南代页1井下石炭统打屋坝组页岩气地质条件及勘探前景          下载免费PDF全文

卢树藩  何犇  杜胜江 《中国地质调查》2016,3(4):6-11

近年来发现黔南地区下石炭统打屋坝组发育厚度较大的黑色页岩层,该地层已经成为黔南地区重要的页岩气目标地层。为进一步了解该地层的页岩气参数,评价其页岩气勘探潜力,对代页1井打屋坝组黑色页岩进行观察和取样分析,显示该井打屋坝组黑色页岩钻厚为80 m,总体为一套深水陆棚相沉积; 干酪根显微组分以腐泥组、壳质组和镜质组为主,Ⅰ型-Ⅲ型干酪根均有发育,有机碳(TOC)含量主要分布在1.5%3.3%之间,镜质体反射率(R_o)为2.15%2.66%; 矿物组成以石英、黏土矿物为主,脆性矿物(不含方解石)含量在35%64%之间; 含气量在0.494.97 m³/t之间,平均为2.20 m³/t。通过露头剖面观察,显示黔南下石炭统打屋坝组黑色页岩厚度均较大,代页1井含气量较高,有机地化、储集物性参数较好,反映打屋坝组具有良好的勘探前景,可进一步加强该地层的基础地质、页岩储层改造和页岩气富集规律研究工作。  相似文献