Deviation of light curves of gamma-ray burst pulses from standard forms due to the curvature effect of spherical fireballs or uniform jets     

Y.-P. Qin  R.-J. Lu 《Monthly notices of the Royal Astronomical Society》2005,362(3):1085-1098

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Modelling the energy dependencies of high-frequency quasi-periodic oscillations in black hole X-ray binaries     

Piotr T. &#;ycki  rzej Nied&#;wiecki  Ma&#;gorzata A. Sobolewska 《Monthly notices of the Royal Astronomical Society》2007,379(1):123-129

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Gamma-ray burst precursors as the remnant of the thermal radiation initially trapped in the fireball     

Li-Xin Li 《Monthly notices of the Royal Astronomical Society》2007,380(2):621-636

In the standard fireball model of gamma-ray bursts (GRBs), the fireball starts with an optically thick phase. As it expands, the fireball becomes optically thin at some stage. The thermal radiation trapped in the originally opaque fireball then leaks out, producing a transient event. The appearance of the event is investigated in the framework of a homogeneous, spherically symmetric and freely expanding fireball produced instantly by an explosive process without continuous injection of mass and energy. We find that, generally, the event has a time duration shorter than that of the main burst, which is presumably produced by the internal shock after the fireball becomes optically thin. The event is separated from the main burst by a quiescent time interval, and is weaker than the main burst at least in a high-energy band. Hence, the event corresponds to a GRB precursor. The precursor event predicted by our model has a smooth and Fast Rise and Exponential Decay (FRED) shaped light curve, and a quasi-thermal spectrum. Typically, the characteristic blackbody photon energy is in the X-ray band. However, if the distortion of the blackbody spectrum by electron scattering is considered, the characteristic photon energy could be boosted to the gamma-ray band. Our model may explain a class of observed GRB precursors – those having smooth and FRED-shaped light curves and quasi-thermal spectra.  相似文献   

On derivation of EIH (Einstein–Infeld–Hoffman) equations of motion from the linearized metric of general relativity theory     

Victor Brumberg 《Celestial Mechanics and Dynamical Astronomy》2007,99(3):245-252

The half-century old idea of Infeld to use the variational principle of the general relativity field equations is reminded to show that the commonly employed EIH (Einstein–Infeld–Hoffman) equations of motion may be derived from the linearized (weak-field) metric alone. Based on it, the linearized metric might be sufficient for post-Newtonian celestial mechanics and astrometry enabling one to derive the post-Newtonian equations of motion and rotation of celestial bodies as well as the post-Newtonian equations of light propagation within the general relativity framework.  相似文献   

The first high-amplitude δ Scuti star in an eclipsing binary system     

J. L. Christiansen  A. Derekas  M. C. B. Ashley  J. K. Webb  M. G. Hidas  D. W. Hamacher  L. L. Kiss 《Monthly notices of the Royal Astronomical Society》2007,382(1):239-244

Consider radar ranging of a distant galaxy in a Friedman–Lemaître cosmological model. In this model the comoving coordinate of the galaxy is constant; hence, the equations of null geodesics for photons travelling to the distant galaxy and back imply Here, τ_e, τ_r and τ_o are, respectively, the times of emission, reflection and observation of the reflected photons, and a (τ) is the scalefactor. Since the Universe is expanding, a (τ) is a monotonically increasing function, so the return traveltime, τ_o−τ_r, must be greater than the forward traveltime, τ_r−τ_e. Clearly, space expands, and on their way back, the photons must travel a longer distance! This paper explains why this argument for the Expansion of Space (EoS) is wrong. We argue that, unlike the expansion of the cosmic substratum, the EoS is unobservable. We therefore propose to apply to it – just like to the ether – Ockham's razor.  相似文献   

A New Formulation for General Relativistic Force-Free Electrodynamics and Its Applications     

Cong Yu 《天体物理学报》2007,7(6):743-756

We formulate the general relativistic force-free electrodynamics in a new 3 ＋ 1 language. In this formulation, when we have properly defined electric and magnetic fields, the covariant Maxwell equations could be cast in the traditional form with new vacuum constitutive constraint equations. The fundamental equation governing a stationary, axisymmetric force-free black hole magnetosphere is derived using this formulation which recasts the Grad-Shafranov equation in a simpler way. Compared to the classic 3＋1 system of Thorne and MacDonald, the new system of 3＋1 equations is more suitable for numerical use for it keeps the hyperbolic structure of the electrodynamics and avoids the singularity at the event horizon. This formulation could be readily extended to non-relativistic limit and find applications in fiat spacetime. We investigate its application to disk wind, black hole magnetosphere and solar physics in both fiat and curved spacetime.  相似文献   

Bounds for mass and rotation of black holes in the observable universe     

A. De Vries  R. Böhme  Th. Schmidt-Kaler 《Astrophysics and Space Science》1995,225(2):221-226

The bounds for the energy change rate of a Maxwell field in the outer space of a rotating black hole, calculated by de Vries (1994) and de Vries (1995), enable us to deduce limits for the rotation and the mass of black holes. For this purpose we assume that a certain part of the anisotropies of the cosmic background radiation is due to absorption or superradiance of black holes (Teukolsky, 1973, Starobinskii and Churilov, 1973). The knowledge of these anisotropies yields bounds for rotation and mass of the black holes in the observable universe.  相似文献   

Relativistic Information Entropy on Uncertainty Analysis   总被引：1，自引：0，他引：1  

Jin Weiliang Han Jie Professor  Dr. -Eng.  Dept. of Civil Engineering  Zhejiang University  Hangzhou  Lecturer. Dept. of Information Science  Electronic Engineering  Zhejiang University  Hangzhou 《中国海洋工程》1996,(4)

- in this paper, a new approach to relativistic information entropy is used to assess some relative uncertainties in structural reliability assessment. This approach is composed of the information theory and the relativistic theory, and can be used to measure the relativity of parameter uncertainty and system uncertainty in structural reliability theory based on the same generalized relativistic reference system. Therefore, the structural reliability assessment can be assessed reasonably by the approach.  相似文献   

An approximate Riemann solver for relativistic magnetohydrodynamics     

A. V. Koldoba  O. A. Kuznetsov  G. V. Ustyugova 《Monthly notices of the Royal Astronomical Society》2002,333(4):932-942

A Godunov-type scheme for relativistic magnetohydrodynamic (MHD) equations is developed. We consider the Maxwell equations and dynamic equations for a gas with perfect conductivity in hyperbolic form as was suggested by van Putten. To calculate the fluxes of conservative variables through cells' interfaces we suggest an algorithm for the solution of the linearized Riemann problem. 'Primitive' variables are calculated by solving a non-linear system using the Newton method .  相似文献   

The maximum mass of neutron stars     

G. Srinivasan 《Astronomy and Astrophysics Review》2002,11(1):67-96

Summary. The maximum mass of neutron stars plays an important role in determining the end point of the evolution of massive stars. As the number of stellar mass black holes in binary x-ray sources grows, and as the mass spectrum of the black holes emerges, the value of the maximum mass of neutron stars has acquired great significance. Although it is now more than sixty years since the first attempt by Oppenheimer and Volkoff, no definitive answer can be given. This review will attempt to outline the main difficulties, both conceptual as well as technical, that stand in the way of a reliable estimate of the maximum mass. We shall also highlight how laboratory experiments, as well as astronomical observations, may help to clarify the true nature of the interior of neutron stars. Received 26 November 2001 / Published online 22 April 2002  相似文献