Photoevaporation of cosmological minihaloes during reionization   总被引：1，自引：0，他引：1  

Paul R. Shapiro  Ilian T. Iliev †  Alejandro C. Raga 《Monthly notices of the Royal Astronomical Society》2004,348(3):753-782

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Non-linear pulsations in differentially rotating neutron stars: mass-shedding-induced damping and splitting of the fundamental mode     

Nikolaos Stergioulas  Theocharis A. Apostolatos  José A. Font 《Monthly notices of the Royal Astronomical Society》2004,352(4):1089-1101

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Laboratory Astrophysics Experiments for Simulation Code Validation: A Case Study     

A. C. Calder 《Astrophysics and Space Science》2005,298(1-2):25-32

The growing field of Laboratory Astrophysics seeks to study the extreme environments found in many astrophysical events in the controlled setting of a laboratory. In addition to the opportunity to perform basic research into the nature and properties of materials in astrophysical environments, laboratory astrophysics experiments serve beautifully for validating calculations performed by simulation codes designed to model astrophysical phenomena. I present results from our ongoing validation effort for FLASH, a parallel adaptive-mesh hydrodynamics code for the compressible, reactive flows of astrophysical environments. The first test case is a laser-driven shock propagating though a multilayer target introducing Rayleigh–Taylor and Richtmyer–Meshkov fluid instabilities at the material interfaces. The second is an accelerating fluid interface that is subject to the Rayleigh–Taylor instability. We found good agreement between simulations and experiment for the multilayer target case, but disagreement between experiment and simulation in the Rayleigh–Taylor case. I discuss our findings and possible reasons for the disagreement.  相似文献   

Including star formation and supernova feedback within cosmological simulations of galaxy formation   总被引：1，自引：0，他引：1  

Scott T.Kay  Frazer R.Pearce  Carlos S.Frenk  AdrianJenkins 《Monthly notices of the Royal Astronomical Society》2002,330(1):113-128

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On the interaction of FR II radio sources with the intracluster medium     

P. Alexander 《Monthly notices of the Royal Astronomical Society》2002,335(3):610-620

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Tidally distorted accretion discs in binary stars     

G. I.Ogilvie 《Monthly notices of the Royal Astronomical Society》2002,330(4):937-949

The non-axisymmetric features observed in the discs of dwarf novae in outburst are usually considered to be spiral shocks, which are the non-linear relatives of tidally excited waves. This interpretation suffers from a number of problems. For example, the natural site of wave excitation lies outside the Roche lobe, the disc must be especially hot, and most treatments of wave propagation do not take into account the vertical structure of the disc.
In this paper I construct a detailed semi-analytical model of the non-linear tidal distortion of a thin, three-dimensional accretion disc by a binary companion on a circular orbit. The analysis presented here allows for vertical motion and radiative energy transport, and introduces a simple model for the turbulent magnetic stress. The   m =2  inner vertical resonance has an important influence on the amplitude and phase of the tidal distortion. I show that the observed patterns find a natural explanation if the emission is associated with the tidally thickened sectors of the outer disc, which may be irradiated from the centre. According to this hypothesis, it may be possible to constrain the physical parameters of the disc through future observations.  相似文献   

Does the plasma composition affect the long-term evolution of relativistic jets?     

L.Scheck  M. A.Aloy  J. M.Martí  J. L.Gómez  E.Müller 《Monthly notices of the Royal Astronomical Society》2002,331(3):615-634

We study the influence of the matter content of extragalactic jets on their morphology, dynamics and emission properties. For this purpose we consider jets of extremely different compositions, including pure leptonic and baryonic plasmas. Our work is based on two-dimensional relativistic hydrodynamic simulations of the long-term evolution of powerful extragalactic jets propagating into a homogeneous environment. The equation of state used in the simulations accounts for an arbitrary mixture of electrons, protons and electron–positron pairs. Using the hydrodynamic models, we have also computed synthetic radio maps and the thermal bremsstrahlung X-ray emission from their cavities.
Although there is a difference of about three orders of magnitude in the temperatures of the cavities inflated by the simulated jets, we find that both the morphology and the dynamic behaviour are almost independent of the assumed composition of the jets. Their evolution proceeds in two distinct epochs. During the first one, multidimensional effects are unimportant and the jets propagate ballistically. The second epoch starts when the first larger vortices are produced near the jet head, causing the beam cross-section to increase and the jet to decelerate. The evolution of the cocoon and cavity is in agreement with a simple theoretical model. The beam velocities are relativistic  ( Γ ≃4)  at kiloparsec scales, supporting the idea that the X-ray emission of several extragalactic jets may be due to relativistically boosted CMB photons. The radio emission of all models is dominated by the contribution of the hotspots. All models exhibit a depression in the X-rays surface brightness of the cavity interior, in agreement with recent observations.  相似文献   

Precessing warped accretion discs in X-ray binaries     

G. I. Ogilvie  G. Dubus 《Monthly notices of the Royal Astronomical Society》2001,320(4):485-503

We study the radiation-driven warping of accretion discs in the context of X-ray binaries. The latest evolutionary equations are adopted, which extend the classical alpha theory to time-dependent thin discs with non-linear warps. We also develop accurate, analytical expressions for the tidal torque and the radiation torque, including self-shadowing.
We investigate the possible non-linear dynamics of the system within the framework of bifurcation theory. First, we re-examine the stability of an initially flat disc to the Pringle instability. Then we compute directly the branches of non-linear solutions representing steadily precessing discs. Finally, we determine the stability of the non-linear solutions. Each problem involves only ordinary differential equations, allowing a rapid, accurate and well-resolved solution.
We find that radiation-driven warping is probably not a common occurrence in low-mass X-ray binaries. We also find that stable, steadily precessing discs exist for a narrow range of parameters close to the stability limit. This could explain why so few systems show clear, repeatable 'superorbital' variations. The best examples of such systems, Her X-1, SS 433 and LMC X-4, all lie close to the stability limit for a reasonable choice of parameters. Systems far from the stability limit, including Cyg X-2, Cen X-3 and SMC X-1, probably experience quasi-periodic or chaotic variability as first noticed recently by Wijers and Pringle. We show that radiation-driven warping provides a coherent and persuasive framework but that it does not provide a generic explanation for the long-term variabilities in all X-ray binaries.  相似文献   

Relativistic gravitational collapse of a cool white dwarf with allowance for the neutronization kinetics     

A. I. Voropinov  M. A. Podurets 《Astronomy Letters》2001,27(6):366-375

We consider and numerically solve the problem of the relativistic gravitational collapse of a spherically symmetric cool nonrotating white dwarf with allowance for the neutronization kinetics. We propose a model equation of state and analyze the neutronization kinetics under simplifying assumptions. A comprehensive mathematical model is constructed for the phenomenon. The system of equations is integrated numerically. The gravitational collapse of a white dwarf that lost its stability is shown to lead to the envelope ejection and to the final state of a hot static neutron star. For comparison, we solve the problem with an equilibrium equation of state. We show that in this case, the entire mass ultimately goes under the gravitational radius to form a black hole.  相似文献   

On rotationally driven meridional flows in stars     

P. Garaud 《Monthly notices of the Royal Astronomical Society》2002,335(3):707-711

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