共查询到20条相似文献，搜索用时 31 毫秒
1.
We calculate the fields surrounding and the power radiated by a slowly rotating neutron star with a frozen-in magnetic dipole field, tilted with respect to the rotation axis, including the effects of spacetime curvature. The general relativistic effects suppress the radiated power relative to flat space by factors up to 1/7 for magnetic dipole radiation and 1/50 for the associated electric quadrupole radiation. This suppression exceeds that which might be expected from a surface red shift alone.Numerical results are found using power series which describe the behavior of electromagnetic fields exterior to a black hole or slowly rotating neutron star. These new solutions, appropriate near the stellar surface, converge for all radii exterior to the neutron star (or black hole) making analytic continuation of the power series unnecessary as well as allowing matching to a linear combination of asymptotic expansions, appropriate for large radius. Typical numerical values for these functions are presented as well as techniques for accelerating the convergence of their respective power series which make them attractive alternatives to numerical integration.Supported in part by NSF Grant PHY 77 28356. 相似文献
2.
We have deduced the intensity spectral function for the spin-flip synchrotron radiation in the presence of a plasma. Using parameters appropriate to astrophysical conditions, we have attempted to compare the characteristics of the spin-flip synchrotron radiation and the normal synchrotron radiation in a magnetized plasma arising from an electron or positron rotating around the magnetic field. A rotating charge gives the maximum possible synchrotron radiative power as compared to a charge of the same energy but moving in a helical path. Since the spin-flip radiational does not depend on the form of the orbital path, whether circular or helical or along a straight line, the analysis presented here gives the lower limit of the relative importance of the spin-flip radiation to the normal synchrotron radiation emitted by the same radiator. 相似文献
3.
本文讨论了共轴、纯转动、force-free的脉冲星系统,在Burman理论基础上建立了一个非共转模型(其中含待定参量,共转情况是它的特例)。利用系统稳定的近似条件——系统能量最小确定特定参量,得到一个与G-J模型类似的共转模型。由于考虑了惯性效应,不存在星风,是稳定态,但没有辐射。在转轴与磁矩有小偏角时,利用非平衡系统更普遍的稳定条件——熵产生最小,确定本模型的参量,得到的辐射能量在量级上与观测值相符合。 相似文献
4.
Pulsars are fast rotating neutron stars with a strong magnetic field, that emit over a wide frequency range. In spite of all efforts during the 40 years after the discovery of pulsars, the mechanism of their radio emission so far remains unknown. We propose a new approach to solving this problem for a subset of pulsars with a high-frequency cutoff of the spectrum from the Pushchino catalogue (the “Pushchino” sample). We provide a theoretical explanation of the observed dependence of the high-frequency cutoff on the pulsar period, and we predict the dependence of the cutoff position from the magnetic field. This explanation is based on a new mechanism for electron radio emission in pulsars. Namely, radiation occurs in the inner (polar) gap, when electrons are accelerated in the electric field that is increasing from zero level at the star surface. In this case the acceleration of electrons passes through a maximum and goes to zero when the electron velocity approaches the speed of light. All the radiated power is located within the radio frequency band. The averaging of radiation intensity over the polar cap, with some natural assumptions of the coherence of the radiation, leads to the observed spectra. It also leads to an acceptable estimate of the power of radio emission. 相似文献
5.
D.J. Scheeres 《Icarus》2007,188(2):430-450
A detailed derivation is given of the effect of solar radiation on the rotational dynamics of asteroids, commonly called the YORP effect. The current derivation goes beyond previous discussions published in the literature and provides a comprehensive secular dynamical analysis of the effect of solar radiation torques acting on a uniformly rotating body, and the evolution of its rotation state over time. Our predicted model has the global radiation properties of the asteroid as explicit parameters, and hence can be specified independent of these parameters. The resulting secular equations for the rotation rate and rotation pole are characterized by three parameters of the body's shape and explicitly includes the effect of thermal inertia on the evolution of these rotation state parameters. With this detailed model, in conjunction with estimated asteroid shapes and poles, we compute the expected YORP torques and dynamic response of several asteroids and the change in rotation rate for specific shapes as a function of obliquity. Finally, we define a convenient dimensionless parameter that is only a function of the body geometry and that can be used to characterize the effects of YORP. 相似文献
6.
《New Astronomy》2013
We investigate the effect of mass on the radiation of a relativistically rotating neutron star. The method of Haxton and Ruffini is used to find the radiation flux from a relativistically rotating neutron star. By extending the idea of a point charge orbiting a black hole, a pulsar is modeled by simulating a relativistically rotating magnetic dipole embedded within a neutron star. The resulting equations retain the mass of the neutron star, thereby introducing effects of general relativity on the radiation from the dipole. We present exact solutions to the modeling equation as well as plots of energy spectra at different rotational velocities and inclination angles. We also present plots of total energy versus mass and two tables containing a comparison of energy ratios. These demonstrate that, for realistic neutron star masses, the high speed enhancement of the radiation is always more than compensated by the frame dragging effect, leading to a net reduction of radiation from the star. It is found that the inclusion of mass not only reduced the special relativistic enhancement, but negates it entirely as the mass of the neutron star approaches the mass limit. 相似文献
7.
It is shown that an outgoing null radiation field in the outer space of a Kerr-Newman black hole is darkened by the rotation
of the black hole. This rotational darkening is calculated for a spheroid emitting null radiation normally to its surface,
yielding the von Zeipel-like effectthat the equatorial region is darkened more strongly than the polar regions.This effect
is not confined to the case of black holes but is also observable for relativistically rotating fluid spheroids such as atmospheres
of pulsars or neutron stars. Moreover, application to Hawking radiation suggests that the black hole cannot be viewed as a
classical black body but that the Hawking radiationis a global geometric effect.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
《Planetary and Space Science》2006,54(9-10):855-870
We develop a model of stochastic radiation pressure for rotating non-spherical particles and apply the model to circumplanetary dynamics of dust grains. The stochastic properties of the radiation pressure are related to the ensemble-averaged characteristics of the rotating particles, which are given in terms of the rotational time-correlation function of a grain. We investigate the model analytically and show that an ensemble of particle trajectories demonstrates a diffusion-like behaviour. The analytical results are compared with numerical simulations, performed for the motion of the dusty ejecta from Deimos in orbit around Mars. We find that the theoretical predictions are in a good agreement with the simulation results. The agreement however deteriorates at later time, when the impact of non-linear terms, neglected in the analytic approach, becomes significant. Our results indicate that the stochastic modulation of the radiation pressure can play an important role in the circumplanetary dynamics of dust and may in case of some dusty systems noticeably alter an optical depth. 相似文献
9.
J. N. Tokis 《Astrophysics and Space Science》1975,36(2):427-438
The general equations of angular momentum and kinetic energy of a rotating deformable (or not rigid) body are discussed for a fixed and a rotating coordinate system. A new system of equations is developed for a deformable body of arbitrary form using the Lagrangian (vector) cisplacement up to the first order terms. The equations are, then, illustrated for a self-gravitating ceformable body perturbed by tides. 相似文献
10.
Xinwu Cao 《Monthly notices of the Royal Astronomical Society》2002,332(4):999-1004
We consider the power of a relativistic jet accelerated by the magnetic field of an accretion disc. It is found that the power extracted from the disc is mainly determined by the field strength and configuration of the field far from the disc. Comparing it with the power extracted from a rotating black hole, we find that the jet power extracted from a disc can dominate over that from the rotating black hole. However, in some cases, the jet power extracted from a rapidly rotating hole can be more important than that from the disc, even if the poloidal field threading the hole is not significantly larger than that threading the inner edge of the disc. The results imply that the radio-loudness of quasars may be governed by its accretion rate, which might be regulated by the central black hole mass. It is proposed that the different disc field generation mechanisms might be tested against observations of radio-loud quasars if their black hole masses are available. 相似文献
11.
S. Mathis T. Decressin A. Palacios P. Eggenberger L. Siess S. Talon C. Charbonnel S. Turck-Chièze J.-P. Zahn 《Astronomische Nachrichten》2007,328(10):1062-1065
Stellar radiation zones are the seat of meridional currents. This circulation has a strong impact on the transport of angular momentum and the mixing of chemicals that modify the evolution of stars. First, we recall in details the dynamical processes that are taking place in differentially rotating stellar radiation zones and the assumptions which are adopted for their modelling in stellar evolution. Then, we present our new results of numerical simulations which allow us to follow in 2D the secular hydrodynamics of rotating stars, assuming that anisotropic turbulence enforces a shellular rotation law and taking into account the transport of angular momentum by internal gravity waves. The different behaviors of the meridional circulation in function of the type of stars which is studied are discussed with their physical origin and their consequences on the transport of angular momentum and of chemicals. Finally, we show how this work is leading to a dynamical vision of the evolution of rotating stars from their birth to their death. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
12.
Hawking’s radiation effect of Klein-Gordon scalar field, Dirac particles and Maxwell’s electromagnetic field in the non-stationary
rotating de Sitter cosmological space-time is investigated by using a method of generalized tortoise co-ordinates transformation.
The locations and the temperatures of the cosmological horizons of the non-stationary rotating de Sitter model are derived.
It is found that the locations and the temperatures of the rotating cosmological model depend not only on the time but also
on the angle. The stress-energy regularization techniques are applied to the two dimensional analog of the de Sitter metrics
and the calculated stress-energy tensor contains the thermal radiation effect. 相似文献
13.
Hamid M. K. Al-Naimiy 《Astrophysics and Space Science》1978,53(1):3-11
The radiation of a charge rotating in a circle with the constant velocity (in the external magnetic field) in the isotropic plasma with random inhomogeneities of the electron density has been considered. A general expression is obtained for the radiation intensity at thenth harmonic, which is a generalization of the known Shott formula. In the ultra-relativistic case the conditions are clarified under which the inhomogeneity effect on the form of the spectrum of radiation from a particle is essential. An asymptotic formula is derived for the spectral intensity in the region of sufficiently low frequencies. The mechanism of transient radiation in this case is shown to prevail over the synchrotron one. 相似文献
14.
Ding-Xiong Wang Wei-Hua Lei Ren-Yi Ma 《Monthly notices of the Royal Astronomical Society》2003,342(3):851-860
The transfer of energy and angular momentum in the magnetic coupling (MC) of a rotating black hole (BH) with its surrounding accretion disc is discussed based on a mapping relation derived by considering the conservation of magnetic flux with two basic assumptions: (i) the magnetic field on the horizon is constant, (ii) the magnetic field on the disc surface varies as a power law with the radial coordinate of the disc. The following results are obtained: (i) the transfer direction of energy and angular momentum between the BH and the disc depends on the position of a co-rotation radius relative to the MC region on the disc, which is eventually determined by the BH spin; (ii) the evolution characteristics of a rotating BH in the MC process without disc accretion are depicted in a parameter space, and a series of values of the BH spin are given to indicate the evolution characteristics; (iii) the efficiency of converting accreted mass into radiation energy of a BH–disc system is discussed by considering the coexistence of disc accretion and the MC process; (iv) the MC effects on disc radiation and the emissivity index are discussed and it is concluded that they are consistent with the recent XMM–Newton observation of the nearby bright Seyfert 1 galaxy MCG–6-30-15 with reference to a variety of parameters of the BH–disc system. 相似文献
15.
Equilibrium models of differentially rotating nascent neutron stars are constructed, which represent the result of the accretion-induced collapse of rapidly rotating white dwarfs. The models are built in a two-step procedure: (1) a rapidly rotating pre-collapse white dwarf model is constructed; (2) a stationary axisymmetric neutron star having the same total mass and angular momentum distribution as the white dwarf is constructed. The resulting collapsed objects consist of a high-density central core of size roughly 20 km, surrounded by a massive accretion torus extending over 1000 km from the rotation axis. The ratio of the rotational kinetic energy to the gravitational potential energy of these neutron stars ranges from 0.13 to 0.26, suggesting that some of these objects may have a non-axisymmetric dynamical instability that could emit a significant amount of gravitational radiation. 相似文献
16.
The equilibria and periodic orbits around a dumbbell-shaped body 总被引：1，自引：0，他引：1
This paper investigates the equilibria, their stability, and the periodic orbits in the vicinity of a rotating dumbbell-shaped body. First, the geometrical model of dumbbell-shaped body is established. The gravitational potential fields are obtained by the polyhedral method for several dumbbell-shaped bodies with various length–diameter ratios. Subsequently, the equilibrium points of these dumbbell-shaped bodies are computed and their stabilities are analyzed. Periodic orbits around equilibrium points are determined by the differential correction method. Finally, in order to understand further motion characteristic of dumbbell-shaped body, the effect of the rotating angular velocity of the dumbbell-shaped bodies is investigated. This study extends the research work of the orbital dynamics from simple shaped bodies to complex shaped bodies and the results can be applied to the dynamics of orbits around some asteroids. 相似文献
17.
We extend to study Hawking radiation via tunneling in conformal gravity. We adopt Parikh-Wilczek’s semi-classical tunneling method and the method of complex-path integral to investigate Hawking radiation from new rotating AdS black holes in conformal gravity. In this paper, the research on Hawking radiation from the rotating black holes is done in a general system, not limited in dragging coordinate systems any longer. Moreover, there existed some shortcomings in the previous derivation of geodesic equations. Different from the massless case, they used a different approach to derive the geodesic equation of the massive particles. Even the treatment was inconsistent with the variation principle of action. To remedy the shortcoming, we improve treatment to deduce the geodesic equations of massive and massless particles in a unified and self-consistent way. In addition, we also recover the Hawking temperature resorting to the complex-path integral method. 相似文献
18.
J. N. Tokis 《Astrophysics and Space Science》1974,31(2):349-362
The aim of the present paper will be to derive an equation of dissipation of energy for a rotating body of arbitrary viscosity distorted by tides, which arise from the gravitational field of its companion in a close pair of such bodies.By a transformation of the fundamental equation of energy dissipation in terms of velocity of tidal deformation (Section 2), the dissipation function is constructed for a tidally-distorted body (Section 3). From this equation, the rate of dissipation of tidal energy is formulated for a nearly-spherical rotating body distorted by second harmonic longitudinal tides (Section 4); the coefficients of viscosity (or the bulk modulus) are treated as arbitrary functions of spatial coordinates. Finally (Section 5), expressions for the total energy dissipation within the orbital cycle are given for axial rotation of the distorted body, provided its angular velocity is constant (for example, with the Keplerian angular velocity).Research financed in part by the Division of Scientific Research and Development of Ministry of Sciences and Culture of Greece. 相似文献
19.
Jack Wisdom 《Icarus》2008,193(2):637-640
Expressions for tidal dissipation in a body in synchronous rotation at arbitrary orbital eccentricity and obliquity are derived. The rate of tidal dissipation for a synchronously rotating body is compared to that in a body in asymptotic nonsynchronous rotation. 相似文献
20.
E. I. Staritsin 《Astronomy Letters》2010,36(11):796-807
An upper limit for the mass loss rate of rapidly rotating main-sequence O9-B4 stars has been determined. Themaximum mass loss
rate of a rotating star is determined by the ability of radiation pressure in lines to remove matter from the gravitational
potential well of the star. The maximum mass loss rate in the case of extremely rapid stellar rotation is a factor of 3–7
higher than that in the case of a nonrotating star. A simple formula for determining the ratio of the maximum mass loss rate
of a rotating star to the maximum mass loss rate of a nonrotating star with the same mass, luminosity, and volume is suggested. 相似文献