共查询到20条相似文献，搜索用时 15 毫秒
1.
对microquaLsar(微类星体)最新的一些研究结果作了比较全面的评述。具有相对论性喷流的microquaLsar在很多现象上类似于极小尺度上的类星体。对X波段的观测可以探测到吸积盘内区甚至接近黑洞的区域。结合低波段上的观测和研究，人们在吸积盘的动力学模型、物质吸积与喷流形成之间的关系以及喷流的超光速运动等方面的认识都有了长足的进步，并且发现了黑洞存在的新证据。对它们的研究为更好地理解河外天体的相对论性喷流和黑洞吸积方面的问题开辟了一条新的途径。 相似文献
2.
Khee-Gan Lee Kinwah Wu Steven V. Fuerst Graziella Branduardi-Raymonl Oliver Crowley 《中国天文和天体物理学报》2009,9(4)
We have calculated the relativistic reflection component of the X-ray spectra of accretion disks in active galactic nuclei (AGN). Our calculations have shown that the spectra can be significantly modified by the motion of the accretion flow, and the gravity and rotation of the central black hole. The absorption edges in the spectra suffer severe en- ergy shifts and smearing, and the degree of distortion depends on the system parameters, in particular, the inner radius of the accretion disk and the disk viewing inclination angles. The effects are significant. Fluorescent X-ray emission lines from the inner accretion disk could be a powerful diagnostic of space-time distortion and dynamical relativistic effects near the event horizons of accreting black holes. However, improper treatment of the re- flection component in fitting the X-ray continuum could give rise to spurious line-like features. These features mimic the true fluorescent emission lines and may mask their relativistic signatures. Fully relativistic models for reflection continua together with the emission lines are needed in order to extract black-hole parameters from the AGN X-ray spectra. 相似文献
3.
The jets observed to emanate from many compact accreting objects may arise from the twisting of a magnetic field threading
a differentially rotating accretion disk which acts to magnetically extract angular momentum and energy from the disk. Two
main regimes have been discussed, hydromagnetic jets, which have a significant mass flux and have energy and angular momentum
carried by both matter and electromagnetic field and, Poynting jets, where the mass flux is small and energy and angular momentum
are carried predominantly by the electromagnetic field. Here, we describe recent theoretical work on the formation of relativistic
Poynting jets from magnetized accretion disks. Further, we describe new relativistic, fully electromagnetic, particle-in-cell
(PIC) simulations of the formation of jets from accretion disks. Analog Z-pinch experiments may help to understand the origin
of astrophysical jets. 相似文献
4.
The stability of the innermost disk region orbiting a Kerr black hole is investigated for geometrically thin accretion disks. The infalling matter transports mass and angular momentum into the Kerr hole. This affects the inner disk boundary and leads to runaway instabilities in some cases. 相似文献
5.
《Chinese Astronomy and Astrophysics》1983,7(1):41-45
We use a rigorous, general relativistic, viscous, fluiddynamical equation to calculate the temperature profile of the accretion disk around a Kerr black hole. Our result shows that there is indeed a maximum in the profile. If the radiation in the disk is black-body radiation, then the result is independent of the viscosity mechanism. Using a free-free radiation and the Lα viscosity law, our results are similar to our previous findings [1]. Our calculation also shows that within the radius of the temperature maximum, there exists a rapidly cooling ring-shaped region, possessing characteristics that are not found in the case with the usual temperature profile. 相似文献
6.
H. G. Paul 《Astronomische Nachrichten》1985,306(3):117-122
The temperature profile of accretion disks moving axially symmetric in the static, spherically symmetric field of a compact, massive object is calculated without specifiing the gravitational theory. Using the covariantly written viscous, fluiddynamical equations of motion, the α viscosity law and free-free radiation of a cooling region is obtained under very general assumptions about the behaviour of the external gravitational field. The used gravitational theory is reflected by inner boundary processes taking place in the region of strong gravity; the cooling region could give a significant „bremsstrahlung”︁ correction to the ”︁cool'' part of the spectrum radiated away from the outer, weak gravity region of the disk. 相似文献
7.
A. N. Semena M. G. Revnivtsev T. I. Larchenkova A. A. Lutovinov 《Astronomy Letters》2017,43(10):677-689
The properties of the aperiodic variability in X-ray binaries with black holes are considered. The power spectra of the luminosity variability for a flat accretion disk that is an emission source with a powerlaw energy spectrum have been modeled. At low frequencies the derived power spectrum has the form of a power law with a slope ? ≈ ?1 and a cutoff at a frequency corresponding to the characteristic frequency of fluctuations at the inner disk edge; at higher frequencies the power spectrum has a complex form. The high-frequency variability is suppressed due to the arrival time delays of photons emerged in different parts of the disk. The presence of azimuthal accretion rate fluctuations in the disk and the disk surface brightness nonuniformity in the observer’s imaginary plane caused by the relativistic effects give rise to an additional variability component at frequencies ～ 200 Hz. 相似文献
8.
研究了环绕致密天体的吸积盘的稳定性质和振动模式。特别关注了在热致和粘滞扰动作用下稳定的对流起支配作用的盘外流。还研究了相对论性吸积盘的振动模式。一些在盘内的捕获的 ,非衰减的模式也许可以用来解释X射线双星和活动星系核中所观测到的准周期振动。 相似文献
9.
We describe a model for SS 433 based on an accretion disk around a black hole. Due to the very high mass transfer rate in the system, the disk must be geometrically thick. Two narrow funnels are formed around the rotation axis and radiation pressure in the funnels accelerates matter to relativistic velocities in the form of two opposite jets. TheX and optical luminosities are evaluated and they agree well with the experimental data. 相似文献
10.
11.
黑洞的吸积是天体物理学中最重要的基础理论之一。近年来该理论取得了引人瞩目的重大进展,具体表现在两个方面。其一是根据黑洞吸积必定跨声速这一特性,提出在一定条件下吸积流中会出现激波,这可称为含激波的吸积理论;其二是基于对一种局域致冷机制-贮导（advection）致冷的作用的重新认识而建立的,称为ADAF理论。在吸积盘的光学厚度很小或很大两种情况下,粘滞产生的大部分热量没有像在标准薄盘模型中那样辐射出去,而是贮存在流体中随流体的径向运动进入黑洞。与标准薄盘模型相比,贮导吸积盘具有高得多的温度和大得多的径向速度,但角动量小于开普勒角动量,吸积致能的效率要低得多。 相似文献
12.
M. G. Revnivtsev R. A. Burenin A. Yu. Tkachenko I. M. Khamitov T. Ak A. Merloni M. N. Pavlinsky R. A. Sunyaev 《Astronomy Letters》2012,38(4):238-248
We present the results of our studies of the aperiodic optical flux variability for SS Cyg, an accreting binary systemwith
a white dwarf. The main set of observational data presented here was obtained with the ANDOR/iXon DU-888 photometer mounted
on the RTT-150 telescope, which allowed a record (for CCD photometers) time resolution up to 8 ms to be achieved. The power
spectra of the source’s flux variability have revealed that the aperiodic variability contains information about the inner
boundary of the optically thick flow in the binary system. We show that the inner boundary of the optically thick accretion
disk comes close to the white dwarf surface at the maximum of the source’s bolometric light curve, i.e., at the peak of the
instantaneous accretion rate onto the white dwarf, while the optically thick accretion disk is truncated at distances 8.5
× 109 cm ∼10R
WD in the low state. We suggest that the location of the inner boundary of the accretion disk in the binary can be traced by
studying the parameters of the power spectra for accreting white dwarfs. In particular, this allows the mass of the accreting
object to be estimated. 相似文献
13.
The secular evolution of the purely general relativistic low angular momentum accretion flow around a spinning black hole is shown to exhibit hysteresis effects. This confirms that a stationary shock is an integral part of such an accretion disc in the Kerr metric. The equations describing the space gradient of the dynamical flow velocity of the accreting matter have been shown to be equivalent to a first order autonomous dynamical systems. Fixed point analysis ensures that such flow must be multi-transonic for certain astrophysically relevant initial boundary conditions. Contrary to the existing consensus in the literature, the critical points and the sonic points are proved not to be isomorphic in general, they can form in a completely different length scales. Physically acceptable global transonic solutions must produce odd number of critical points. Homoclinic orbits for the flow possessing multiple critical points select the critical point with the higher entropy accretion rate, confirming that the entropy accretion rate is the degeneracy removing agent in the system. However, heteroclinic orbits are also observed for some special situation, where both the saddle type critical points of the flow configuration possesses identical entropy accretion rate. Topologies with heteroclinic orbits are thus the only allowed non-removable degenerate solutions for accretion flow with multiple critical points, and are shown to be structurally unstable. Depending on suitable initial boundary conditions, a homoclinic trajectory can be combined with a standard non-homoclinic orbit through an energy preserving Rankine-Hugoniot type of stationary shock, and multi-critical accretion flow then becomes truly multi-transonic. An effective Lyapunov index has been proposed to analytically confirm why certain class of transonic flow cannot accommodate shock solutions even if it produces multiple critical points. 相似文献
14.
The magnetic field in an accretion disk is estimated assuming that all of the angular momentum within prescribed accretion
disk radii is removed by a jet. The magnetic field estimated at the base of the jet is extrapolated to the blazar emission
region using a model for a relativistic axisymmetric jet combined with some simplifying assumptions based on the relativistic
nature of the flow. The extrapolated magnetic field is compared with estimates based upon the synchrotron and inverse Compton
emission from three blazars, MKN 501, MKN 421 and PKS 2155-304. The magnetic fields evaluated from pure synchrotron self-Compton
models are inconsistent with the magnetic fields extrapolated in this way. However, in two cases inverse Compton models in
which a substantial part of the soft photon field is generated locally agree well, mainly because these models imply magnetic
field strengths consistent with an important Poynting Flux component. This comparison is based on estimating the mass accretion
rate from the jet energy flux. Further comparisons along these lines will be facilitated by independent estimates of the mass
accretion rate in blazars and by more detailed models for jet propagation near the black hole. 相似文献
15.
汪定雄 《中国天文和天体物理学报》1999,(4)
对黑洞吸积盘内区温度的径向分布特征和演化特征作了详细的讨论．结果表明：（１）盘内区的温度并非随径向坐标ｒ单调减少,在接近盘的内边缘处有一个盘温的峰值环．在盘温的峰值环和盘的内边缘之间形成一个温度梯度很大的冷却区;（２）在盘吸积的过程中,盘内区温度的峰值和冷却区的平均温度梯度均随中心黑洞的无量纲角动量ａ的增加而单调增加,而金温峰值环半径和冷却区的径向宽度均随ａ的增加而单调减小;（３）盘的热辐射光度随ａ的增加而单调增加． 相似文献
16.
17.
《Chinese Astronomy and Astrophysics》2005,29(2):113-119
Using the standard Runge-Kutta method, a global solution of the basic equations describing black hole accretion flows is derived. It is proved that transition from a standard thin disk to an advection-dominated accretion flow is realizable in case of high viscosity, without introducing any additional mechanism of energy transfer or specifying any ad hoc outer boundary condition. 相似文献
18.
A. S. Zentsova 《Astrophysics and Space Science》1983,95(2):459-462
A hypothesis is being put forward that the formation of jets in the nuclei of radio galaxies is due to a high-speed energy excretion (explosion) in the accretion disk around a massive black hole. The explosion can be induced, for example, by a fall of the star into the black hole. For the accretion disk featuring an exponential high-density distribution, an asymmetrical explosion can be obtained: the shock front moves in the direction of decreasing the density accelerately and achieves the relativistic velocity swiftly, carrying away the most fraction of the explosion energy. Radio emission of the jet involves synchrotron radiation of relativistic electrons which are accelerated by such shock wave in the magnetic field driven up by the shock front. 相似文献
19.
D.V. Bisikalo A.A. Boyarchuk V.M. Chechetkin O.A. Kuznetzov 《Astrophysics and Space Science》1997,252(1-2):389-397
The results of two-dimensional, non-adiabatic gas dynamical simulations of gas flows in symbiotic stars are presented. It is shown that for a binary system with components that do not fill their Roche lobes, the structure of the gaseous stream is determined not only by the flow from the vicinity of the inner Lagrangian point, but also by the flow of matter caused by the orbital motion of the accretor through the gas of the stellar wind.The calculated gaseous flow structure consists of a set of shocks and tangential discontinuities. It is found that for all considered cases two bow shocks exist. One of the bow shocks is located in front of the accretor in the path of its orbital motion, and the second one is between the components.It is found that matter is accreted in a spiral fashion, forming an accretion disk. In steady-state simulations, a structure with shocks (both trailing and leading) in the disk was observed. Gas dynamical perturbations of the disk's outer edge by the accreting gas inflow lead to the formation of two intensive trailing shocks propagating inward. Gas dynamical perturbations of the inner part of the disk result in the occurrence of leading shocks. One possible mechanism for the generation of spiral shocks is dissipative instability. The existence of spiral shocks results in a redistribution of the angular momentum of the disk material and an increase of the accretion rate. 相似文献
20.
中子星X射线双星中kHz QPO现象的理论解释 总被引：1，自引：0，他引：1
罗西X射线时变探测器(RXTE)在中子星小质量X射线双星中发现了千赫兹准周期振荡现象(kHzQPO)。kHzQPO的频率一般在几百到上千赫兹,其动力学时标与吸积盘最内部区域物质的运动时标一致,因此普遍认为kHz QPO产生于中子星表面附近区域,携带了来自中心中子星及周围强引力场信息,如质量、自转周期、角动量、半径、磁场等。kHz QpO现象的理解为研究强引力场和致密物质状态开启了一扇新的窗口。着重介绍基于kHz QPO的基本现象和相应的理论模型。 相似文献