共查询到20条相似文献，搜索用时 328 毫秒
1.
Janet E. Drew Daniel Proga & James M. Stone 《Monthly notices of the Royal Astronomical Society》1998,296(1):L6-L10
The generation of magnetic fields by a battery, operating in an ion–electron plasma around a Kerr black hole, is studied in the 3+1 split of the Kerr metric. It is found that the gravitomagnetic contributions to the electron partial pressure are able to drive currents. The strength of the equilibrium magnetic field should be higher than for the classical Biermann battery, which is found to operate in this relativistic context as well, since the gravitomagnetic driving terms can less easily be quenched than the classical ones. In axisymmetry the battery can induce only toroidal magnetic fields. Once a toroidal magnetic field is present, however, the coupling of gravitomagnetic and electromagnetic fields generates a poloidal magnetic field even in axisymmetry. A rotating black hole, embedded in plasma, will therefore always generate toroidal and poloidal magnetic fields. 相似文献
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Profiles of spectral lines emitted from an accretion ring around an object with strong gravitational field should be affected by Doppler shift, gravitational redshift, and deflection of light. Taking these effects into account, precise line profile of a Keplerian ring around a Kerr black hole for a distant observer is obtained by solving the kinetic equation of photons. 相似文献
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We have obtained a solution of the Dirac equation near the horizon of a Kerr-Newman black hole and compared it with the solution of the Klein-Gordon equation. We first generalized the work of LIU Liao and XU Dian-yan for a quasi-extreme Kerr black hole to a quasi-extreme Kerr-Newman black hole, then further generalized to a general Kerr-Newman black hole, and thereby verified that the Dirac particles emitted by a general Kerr-Newman black hole do have a black-body energy spectrum. 相似文献
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We present numerical simulations of the axisymmetric accretion of a massive magnetized plasma torus on a rotating black hole. We use a realistic equation of state, which takes into account neutrino cooling and energy loss due to nucleus dissociations. The calculation are performed in the ideal relativistic MHD approximation using an upwind conservative scheme that is based on a linear Riemann solver and the constrained transport method to evolve the magnetic field. The gravitational attraction of the black hole is introduced via the Kerr metric in the Kerr–Schild coordinates. We simulate various magnetic field configurations and torus models, both optically thick and thin for neutrinos.We have found an effect of alternation of the magnetic field orientation in the ultrarelativistic jet formed as a result of the collapse. The calculations show evidence for heating of the wind surrounding the collapsar by the shock waves generated at the jet–wind border. It is shown that the neutrino cooling does not significantly change either the structure of the accretion flow or the total energy release of the system. The angular momentum of the accreting matter defines the time scale of the accretion. Due to the absence of the magnetic dynamo in our calculations, the initial strength and topology of the magnetic field determines the magnetization of the black hole, jet formation properties and the total energy yield. We estimate the total energy of accretion which transformed to jets as 1.3 × 1052 ergs which was sufficient to explain hypernova explosions like GRB 980425 or GRB 030329. 相似文献
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In this paper, we critically discuss the so-far performed attempts aimed at the detection of the general relativistic gravitomagnetic Lense–Thirring effect in the gravitational field of the Earth with the existing LAGEOS satellites. In the latest reported measurement of the gravitomagnetic shift with the nodes of the LAGEOS satellites and the second generation GRACE-only EIGEN-GRACE02S Earth gravity model over an observational time span of 11 years a 5–10% total accuracy is claimed at 1–3σ, respectively. We will show that, instead, it might be 15–45% (1–3σ) if the impact of the secular variations of the even zonal harmonics is considered. Possible strategies in order both to make more robust and reliable the tests with the node-only LAGEOS–LAGEOS II combination used and to overcome the problems affecting it with other alternative combinations are presented. 相似文献
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The equation of motion written down using a metric obtained from the Kerr metric allows us to get both the deflection angle of light ray bending by the gravitational field of the Sun and its corresponding time delay. We reproduce the experimental data of Epstein-Shapiro and also it is in accordance with the theoretical results obtained by Brumberget al. (1990) using another approach to this problem.Presented at the 2nd UN/ESA Workshop, held in Bogotá, Colombia, 9–13 November, 1992. 相似文献
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K. H. Lotze 《Astrophysics and Space Science》1986,120(2):191-204
In this paper we investigate the combined influence of both cosmological and electromagnetic particle creation mechanisms upon massive particles with spin 1/2 on the basis of general covariant Dirac theory.Curved space-time, a radiation-dominated Friedmann universe, is treated as an unquantized gravitational field and the low-frequency part of the 2.7 K background radiation is approximated by homogeneous, constant, and parallel external electric and magnetic fields. We calculate the number density of spin 1/2 particles with massm which are created under the influence of both these external fields.We find that the electric field and the magnetic field both amplify the genuine, purely gravitational particle production. This influence of the magnetic field, which is in contrast to its reducing effect as far as the creation of spin-zero particles is concerned, can clearly be traced back to its coupling to the spin of the particles.Under certain conditions the electromagnetic fields in the early universe can influence the particle creation process even more than the gravitational field. 相似文献
9.
N. R. Sibgatullin 《Astronomy Letters》2002,28(2):83-88
We derive a formula for the nodal precession frequency and the Keplerian period of a particle at an arbitrary orbital inclination (with a minimum latitudinal angle reached at the orbit) in the post-Newtonian approximation in the external field of an oblate rotating neutron star (NS). We also derive formulas for the nodal precession and periastron rotation frequencies of slightly inclined low-eccentricity orbits in the field of a rapidly rotating NS in the form of asymptotic expansions whose first terms are given by the Okazaki-Kato formulas. The NS gravitational field is described by the exact solution of the Einstein equation that includes the NS quadrupole moment induced by rapid rotation. Convenient asymptotic formulas are given for the metric coefficients of the corresponding space-time in the form of Kerr metric perturbations in Boyer-Lindquist coordinates. 相似文献
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The effect of a time-dependent cosmological constant is considered in a family of scalar-tensor theories. The Bianchi type I, III, V, VIo and Kantowski-Sachs models for vacuum and perfect fluid matter are found. The gravitational constant decreases with time so that these models satisfy the Dirac hypothesis. The “cosmological constant” also decreases with time, therefore it can have a very small value at the present time. 相似文献
13.
Lorenzo Iorio Herbert I. M. Lichtenegger Matteo Luca Ruggiero Christian Corda 《Astrophysics and Space Science》2011,331(2):351-395
Recent years have seen increasing efforts to directly measure some aspects of the general relativistic gravitomagnetic interaction
in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical
point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions
of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus
on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate
the present and future perspectives in directly measuring such an elusive relativistic effect. 相似文献
14.
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
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M. Sereno 《Monthly notices of the Royal Astronomical Society》2007,380(3):1023-1028
Gravitational lensing provides an efficient tool for the investigation of matter structures, independent of the dynamical or the hydrostatic equilibrium properties of the deflecting system. However, it depends on the kinematic status. In fact, either a translational motion or a coherent rotation of the mass distribution can affect the lensing properties. Here, light deflection by galaxy clusters in motion is considered. Even if gravitational lensing mass measurements of galaxy clusters are regarded as very reliable estimates, the kinematic effect should be considered. A typical peculiar motion with respect to the Hubble flow brings about a systematic error ≲0.3 per cent, independent of the mass of the cluster. On the other hand, the effect of the spin increases with the total mass. For cluster masses ∼1015 M⊙ , the effect of the gravitomagnetic term is ≲0.04 per cent on strong lensing estimates and ≲0.5 per cent in the weak-lensing analyses. The total kinematic effect on the mass estimate is then ≲1 per cent, which is negligible in current statistical studies. In the weak-lensing regime, the rotation imprints a typical angular modulation in the tangential shear distortion. This would allow, in principle, a detection of the gravitomagnetic field and a direct measurement of the angular velocity of the cluster but the required background source densities are well beyond current technological capabilities. 相似文献
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We discuss the evolution of the massive Dirac particle in the cosmic magnetic field. The magnetic field makes the space metric anisotropic. By solving the Dirac equation we obtain the apparent magnetic moment of the neutrino in the cosmic magnetic field. 相似文献
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We study spherically symmetrical equilibrium states of collisionless stellar systems confined to a spherical box. These equilibrium states correspond to the statistics introduced by Lynden-Bell in his theory of 'violent relaxation', and are described by a Fermi–Dirac distribution function. We compute the corresponding equilibrium diagram and show that a global entropy maximum exists for any accessible control parameter. This equilibrium state shows a pronounced separation between a degenerate core and a halo. We therefore check that degeneracy is able to stop the gravitational collapse (of a collisionless system), and we propose a simple model for the 'core–halo' structure. We also discuss the relevance of our study for real galaxies or other astrophysical systems such as massive neutrinos. 相似文献
19.
A. A. Abdujabbarov A. A. Tursunov B. J. Ahmedov A. Kuvatov 《Astrophysics and Space Science》2013,343(1):173-179
The collision of test charged particles in the vicinity of an event horizon of a weakly magnetized non-rotating black hole with gravitomagnetic charge has been studied. The presence of the external magnetic field decreases the innermost stable circular orbits (ISCO) radii of charged particles. The opposite mechanism occurs when there is nonvanishing gravitomagnetic charge. For a collision of charged particle moving at ISCO and the neutral particle falling from infinity the maximal collision energy can be decreased by gravitomagnetic charge in the presence of external asymptotically uniform magnetic field. 相似文献
20.
极端质量比旋进系统是空间引力波探测器最重要的波源之一。对引力波的探测需要高精度波形模版。当前主流的极端质量比旋进系统引力波计算模型中,人们一般将小质量天体当作试验粒子进行计算,而忽略了其结构及自身引力对背景引力场的影响。利用Mathisson-Papapetrou-Dixon方程研究延展体在弯曲时空中的运动,以及小天体自旋和质量多极矩对引力波信号识别产生的影响。结果表明,质量比在10?6-10?4范围的旋进系统,其自旋达到很大时,自旋对延展体的轨道运动有不可忽略的影响;在质量比10?4-10?2区间内,需要考虑中心黑洞潮汐作用导致的白矮星形变;在质量比大于10?4,且白矮星自旋很大时,其自旋产生的形变会对小天体轨道运动产生不可忽略的影响。大质量黑洞潮汐作用导致的恒星级黑洞或中子星产生的形变可以忽略,中子星和黑洞的自旋会对轨道运动产生不可忽略的影响,而自旋产生的四极矩对轨道运动不产生影响。 相似文献