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1.
<正>活动星系核(中心黑洞质量M_(BH)～10~6-10~(10)M_⊙)和黑洞X射线双星(M_(BH)～10M_⊙)普遍被认为具有相似的中心引擎:黑洞、吸积盘和喷流.类似的中心引擎、质量相却差如此之大(6–9个数量级)的两类黑洞系统是否具有相似的物理仍不清楚.本文围绕不同尺度黑洞天体的物理性质和观测特性展开,主要研究了不同尺度黑洞天体活动的基本面关系以及黑洞X射线双星的能谱演化. 相似文献
2.
活动星系核有两种主要的光变:不规则的闪耀和比较有规律的周期性光变,不规则光变的典型的时间尺度是10~4—10~5秒,周期性光变的典型的时间尺度是10~6—10~8秒。这篇综述主要讨论基于活动星系核黑洞吸积模型上的一些光变模型。这些讨论表明,活动星系核的短时标光变特征对厚吸积盘模型提供了强有力的支持。对时标较长的周期性光变,尽管现在已有不少模型(“亮斑”、薄盘的不稳定性、双稳定性、自引力吸积盘的脉动等等),但是所有这些模型都不够完善;当然也有些模型是很有希望的(如双稳定性)。 相似文献
3.
通过收集数据,用标准α盘模型法、短时标光变法、连续波混响滞后法、微引力透镜法分析了活动星系核吸积盘辐射区半径,并对4种方法进行分析讨论。结果表明:(1)将耀变体和类星体参数比较,发现两个子类的中心黑洞质量、光度和吸积盘辐射区半径都没有明显差别。选择高光度源进行研究,出现了两个子类以上参数无明显区别的情况;(2)短时标光变法得到的吸积盘辐射区半径比和黑洞质量没有明显的相关性;(3)连续波混响滞后法得到的吸积盘辐射区半径比对黑洞质量的依赖性高于标准α盘模型法,对于无法确定中心黑洞质量的源,可以利用连续波混响滞后法得到吸积盘辐射区半径;(4)微引力透镜法得到的吸积盘辐射区半径比和黑洞质量没有明显的相关性,且该方法只适用于存在微引力透镜效应的类星体;(5)这些方法从观测上证明了吸积盘辐射区半径与黑洞质量存在相关性,验证了标准模型成立。为进一步在观测上寻找这4种方法所需要的源提供了理论指导,对活动星系核的吸积盘辐射区半径研究有重要意义。 相似文献
4.
给出的 2 3个BLLac天体的Hβ发射线光度分布呈现双峰结构 ,研究表明 :对于Hβ发射线光度大于 1 0 4 1ergs- 1的BLLac天体 ,其中央黑洞吸积盘很可能是标准盘。而对于Hβ发射线光度小于 1 0 4 1ergs- 1的BLLac天体 ,其中央黑洞吸积流已从标准盘转变为ADAF .本文提出了一种估计BLLac天体中央黑洞质量的新方法。 相似文献
5.
本文利用含平流的热吸积流的自相似解,在电子对为非热产生的情况下,求得了含平流的热单温吸积流在小吸积率时的径向结构．证实了含平流热吸积流所具有的显著特征和基本性质,并得到一些新的结果：含平流的热吸积流存在一个临界半径r,含平流热吸积流的辐射冷却率与中心天体的质量成平方反比关系,含平流热吸积的电子对密度高于SLE模型吸积盘． 相似文献
6.
《天文学进展》2019,(4)
黑洞是广义相对论理论预言的天体,也是很多天文现象,如类星体、活动星系核、喷流、吸积盘的中心引擎。根据广义相对论,宇宙中的黑洞可以由质量和自旋两个参数来描述。对比黑洞质量的测定,自旋的测量较为困难。但自旋的方向与很多天文现象密切相关。如果黑洞自旋方向与吸积盘的转动方向一致,将形成正向吸积的天文现象;反之,如果黑洞自旋的与吸积盘的转动方向相反,将形成逆向吸积的天文现象。利用宽线区尺度与光学光度之间的关系,最近的研究发现了逆向吸积盘的可能候选体。利用双黑洞并合的物理图像提出了一种逆向吸积盘的物理形成机制,并定量计算了相关的逆向吸积盘形成率。发现了超大质量双黑洞系统的质量比分布与类星体逆向吸积盘的形成率之间存在定量关系,该定量关系可以通过未来的空间引力波探测以及逆向吸积盘的探测进行检验。 相似文献
7.
自转作为描述黑洞天体物理性质的两个基本参数之一,其研究正方兴未艾.本文以星系中心超大质量黑洞(SMBH)的自转为研究主题,阐述自转的确定、宇宙学演化及其对黑洞吸积历史的限制.SMBH附近的加速机制使粒子产生甚高能量的辐射,对这些辐射的观测可以给出中心黑洞的信息.基于此,我们提出了利用TeV光变限制黑洞自转参数的方法.基本原理是:TeV光变给出了辐射区域最大尺度的限制,吸积盘辐射场通过对TeV光子的吸收光深给出了辐射区域最小尺度的限制.由于吸积盘辐射场与黑洞自转直接相关,从而结合TeV光变可以限制黑洞自转.对于给定的光度,快 相似文献
8.
汪定雄 《中国天文和天体物理学报》1996,(4)
本文详细讨论了在Blandford－Znajek过程中吸积盘中心黑洞的角动量和质量的总变化率与质量吸积率和能量提取率之比的关系，在此基础上讨论了BlandfordZnajek过程对黑洞吸积盘内边缘半径r_(ms)演化的影响，并证明在此过程中中心黑洞的熵总是增大的。 相似文献
9.
对自引力磁均分和磁守恒两种模型的径向振荡稳定性的研究表明：在同时考虑自引力和磁场作用的情况下,吸积盘在磁均分和磁守恒模型中均存在着三种振荡模式,其中粘滞模式总是稳定的,磁声模式是不稳定的,中性模式在图中较长波段范围趋于稳定,在较短波段范围是不稳定的．这些结果有利于解释活动天体的Mark421和Pks2155—304的长周期光变现象．同时阐明了自引力在两种模型中对三种模式的影响有相同的趋势,而对磁场则分别起着相反的作用．这个结论表明磁均分吸积盘模型在解释光变现象时更为有利． 相似文献
10.
收集了47个Blazar天体的短时标光变资料,估算了中心天体质量和不同波段辐射区域,并对估算结果作了统计分析,发现Blazar天体中心黑洞质量在10~7M_☉到10~(10)M_☉之间,BL Lac天体与平谱射电类星体中心黑洞质量有很大差异,平谱射电类星体中心黑洞质量大于BL Lac天体中心黑洞质量;红外波段和γ射线波段辐射区域大小相似.同时,利用收集到Blazar天体的热光度分析了Blazar天体热光度与短时标光变之间的关系,证实了射电选BL Lac(RBL)天体和平谱射电类星体(FSRQs)的辐射是强成束的,但相对论聚柬效应对X射线选BL Lac(XBL)天体的辐射影响较小. 相似文献
11.
This paper studies the properties of self-gravity of accretion discs around supermassive black holes. With integration on the thin disc configuration, this paper has calculated the radial and vertical components of self-gravity of accretion discs. The discussion mainly concentrates on the radial component, and the results are briefly as follows: for accretion discs around supermassive black holes (M10
8–1010 M). At the distance where (R/R
g)105–104, the radial component of self-gravity dominates over the central one where the dynamical structure of the accretion discs completely differs from that of Keplerian disc. A turbulence driven by radial self-gravity instability as a kind of energy source is proposed. This paper has two criteria for the comparison of magnitude between the self-gravity of accretion discs and the gravity of the central black hole, from which an analytic estimation for the outer radius of the accretion discs has been derived. The results of this paper may be used to explain the accretion discs of quasars and AGNs.This research was supported by the National Natural Science Foundation of China. 相似文献
12.
A. Ulubay-Siddiki O. Gerhard M. Arnaboldi 《Monthly notices of the Royal Astronomical Society》2009,398(2):535-547
We consider warped equilibrium configurations for stellar and gaseous discs in the Keplerian force field of a supermassive black hole, assuming that the self-gravity of the disc provides the only acting torques. Modelling the disc as a collection of concentric circular rings and computing the torques in the non-linear regime, we show that stable, strongly warped precessing equilibria are possible. These solutions exist for a wide range of disc-to-black-hole mass ratios M d / M bh , can span large warp angles of up to ±∼120° , have inner and outer boundaries, and extend over a radial range of a factor of typically two to four. These equilibrium configurations obey a scaling relation such that in good approximation where is the (retrograde) precession frequency and Ω is a characteristic orbital frequency in the disc. Stability was determined using linear perturbation theory and, in a few cases, confirmed by numerical integration of the equations of motion. Most of the precessing equilibria are found to be stable, but some are unstable. The main result of this study is that highly warped discs near black holes can persist for long times without any persistent forcing other than by their self-gravity. The possible relevance of this to galactic nuclei is briefly discussed. 相似文献
13.
M. Reyes-Ruiz 《Monthly notices of the Royal Astronomical Society》2007,380(1):311-319
We study the viscous evolution of protoplanetary discs driven by the combined action of magnetohydrodynamic turbulence, resulting from the magneto-rotational instability (MRI), self-gravity torques, parametrized in terms of an effective viscosity and an additional viscous agent of unspecified origin. The distribution of torques driving the evolution of the disc is calculated by analysing where in the disc the MRI develops and, to incorporate the effect of self-gravity, calculating the Toomre parameter. We find that, generally, discs rapidly evolve towards a configuration where the intermediate regions, from a fraction of an au to a few au, are stable against the MRI due to their low-ionization degree. As an additional source of viscosity is assumed to operate in those regions, subsequent evolution of the disc is eruptive. Brief episodes of high mass accretion ensue as the criterion for the development of the MRI is met in the low-ionization region. The radial distribution of mass and temperature in the disc differs considerably from disc models with constant α parameter or layered accretion models, with potentially important consequences on the process of planet formation. 相似文献
14.
Maxim Lyutikov 《Monthly notices of the Royal Astronomical Society》2009,396(3):1545-1552
Strong magnetic fields modify particle motion in the curved space–time of spinning black holes and change the stability conditions of circular orbits. We study conditions for magnetocentrifugal jet launching from accretion discs around black holes, whereby large-scale black hole lines anchored in the disc may fling tenuous coronal gas outwards. For a Schwarzschild black hole, magnetocentrifugal launching requires that the poloidal component of magnetic fields makes an angle less than 60° to the outward direction at the disc surface, similar to the Newtonian case. For prograde rotating discs around Kerr black holes, this angle increases and becomes 90° for footpoints anchored to the disc near the horizon of a critically spinning a = M black hole. Thus, a disc around a critically spinning black hole may centrifugally launch a jet even along the rotation axis. 相似文献
15.
W. K. M. Rice Philip J. Armitage 《Monthly notices of the Royal Astronomical Society》2009,396(4):2228-2236
Angular momentum transport within young massive protoplanetary discs may be dominated by self-gravity at radii where the disc is too weakly ionized to allow the development of the magneto-rotational instability. We use time-dependent one-dimensional disc models, based on a local cooling time calculation of the efficiency of transport, to study the radial structure and stability (against fragmentation) of protoplanetary discs in which self-gravity is the sole transport mechanism. We find that self-gravitating discs rapidly attain a quasi-steady state in which the surface density in the inner disc is high and the strength of turbulence very low ( α∼ 10−3 or less inside 5 au). Temperatures high enough to form crystalline silicates may extend out to several astronomical units at early times within these discs. None of our discs spontaneously develop regions that would be unambiguously unstable to fragmentation into substellar objects, though the outer regions (beyond 20 au) of the most massive discs are close enough to the threshold that fragmentation cannot be ruled out. We discuss how the mass accretion rates through such discs may vary with disc mass and with mass of the central star, and note that a determination of the relation for very young systems may allow a test of the model. 相似文献
16.
U. S. Pandey 《Astrophysics and Space Science》1987,137(1):77-84
We present a survey of accretion disc models around compact objects — in particular the accretion onto white dwarfs, neutron stars, and black holes. We discuss both the thin disc as well as thick disc models and also the feaibility where either of these can be applied in the astrophysical systems. The crucial role of magnetic field in facilitating the formation of accretion discs in neutron stars is indicated. The prime significance of accretion discs in the generation of soft and hard X-rays is also discussed. Thick disc models are found to explain the observations of active galactic nuclei and also collimated and persistent jets in some of the radio sources. 相似文献
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18.
We present Fe Kα line profiles from and images of relativistic discs with finite thickness around a rotating black hole using a novel code. The line is thought to be produced by iron fluorescence of a relatively cold X-ray-illuminated material in the innermost parts of the accretion disc and provides an excellent diagnostic of accretion flows in the vicinity of black holes. Previous studies have concentrated on the case of a thin, Keplerian accretion disc. This disc must become thicker and sub-Keplerian with increasing accretion rates. These can affect the line profiles and in turn can influence the estimation of the accretion disc and black hole parameters from the observed line profiles. We here embark on, for the first time, a fully relativistic computation which offers key insights into the effects of geometrical thickness and the sub-Keplerian orbital velocity on the line profiles. We include all relativistic effects such as frame-dragging, Doppler boost, time dilation, gravitational redshift and light bending. We find that the separation and the relative height between the blue and red peaks of the line profile diminish as the thickness of the disc increases. This code is also well suited to produce accretion disc images. We calculate the redshift and flux images of the accretion disc and find that the observed image of the disc strongly depends on the inclination angle. The self-shadowing effect appears remarkable for a high inclination angle, and leads to the black hole shadow being in this case, completely hidden by the disc itself. 相似文献
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20.
We present results from a numerical study of the runaway instability of thick discs around black holes. This instability is an important issue for most models of cosmic gamma-ray bursts, where the central engine responsible for the initial energy release is such a system consisting of a thick disc surrounding a black hole. We have carried out a comprehensive number of time-dependent simulations aimed at exploring the appearance of the instability. Our study has been performed using a fully relativistic hydrodynamics code. The general relativistic hydrodynamic equations are formulated as a hyperbolic flux-conservative system and solved using a suitable Godunov-type scheme. We build a series of constant angular momentum discs around a Schwarzschild black hole. Furthermore, the self-gravity of the disc is neglected and the evolution of the central black hole is assumed to be that of a sequence of exact Schwarzschild black holes of varying mass. The black hole mass increase is thus determined by the mass accretion rate across the event horizon. In agreement with previous studies based on stationary models, we find that by allowing the mass of the black hole to grow the disc becomes unstable. Our hydrodynamical simulations show that for all disc-to-hole mass ratios considered (between 1 and 0.05), the runaway instability appears very fast on a dynamical time-scale of a few orbital periods, typically a few 10 ms and never exceeding 1 s for our particular choice of the mass of the black hole (2.5 M-3 M-1 ) . The implications of our results in the context of gamma-ray bursts are briefly discussed. 相似文献