Solving linearized equations of the N-body problem using the Lie-integration method     

András Pál  Áron Süli 《Monthly notices of the Royal Astronomical Society》2007,381(4):1515-1526

Several integration schemes exist to solve the equations of motion of the N -body problem. The Lie-integration method is based on the idea to solve ordinary differential equations with Lie-series. In the 1980s, this method was applied to solve the equations of motion of the N -body problem by giving the recurrence formulae for the calculation of the Lie-terms. The aim of this work is to present the recurrence formulae for the linearized equations of motion of N -body systems. We prove a lemma which greatly simplifies the derivation of the recurrence formulae for the linearized equations if the recurrence formulae for the equations of motions are known. The Lie-integrator is compared with other well-known methods. The optimal step-size and order of the Lie-integrator are calculated. It is shown that a fine-tuned Lie-integrator can be 30–40 per cent faster than other integration methods.  相似文献   

The Millennium Galaxy Catalogue: the local supermassive black hole mass function in early- and late-type galaxies     

Alister W. Graham  Simon P. Driver  Paul D. Allen  Jochen Liske 《Monthly notices of the Royal Astronomical Society》2007,378(1):198-210

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Gravitational wave bursts from the Galactic massive black hole     

Clovis Hopman  Marc Freitag  Shane L. Larson 《Monthly notices of the Royal Astronomical Society》2007,378(1):129-136

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Horizon-penetrating transonic accretion discs around rotating black holes     

Rohta Takahashi 《Monthly notices of the Royal Astronomical Society》2007,382(2):567-593

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Stellar-mass black hole binaries as ultraluminous X-ray sources     

S. A. Rappaport  Ph. Podsiadlowski  E. Pfahl † 《Monthly notices of the Royal Astronomical Society》2005,356(2):401-414

Ultraluminous X-ray sources (ULXs) with   L _x > 10³⁹ erg s⁻¹  have been discovered in great numbers in external galaxies with ROSAT , Chandra and XMM-Newton . The central question regarding this important class of sources is whether they represent an extension in the luminosity function of binary X-ray sources containing neutron stars and stellar-mass black holes (BHs), or a new class of objects, e.g. systems containing intermediate-mass BHs  (100–1000 M_⊙)  . We have carried out a theoretical study to test whether a large fraction of the ULXs, especially those in galaxies with recent star formation activity, can be explained with binary systems containing stellar-mass BHs. To this end, we have applied a unique set of binary evolution models for BH X-ray binaries, coupled to a binary population synthesis code, to model the ULXs observed in external galaxies. We find that for donor stars with initial masses  ≳10 M_⊙  the mass transfer driven by the normal nuclear evolution of the donor star is sufficient to potentially power most ULXs. This is the case during core hydrogen burning and, to an even more pronounced degree, while the donor star ascends the giant branch, although the latter phases last only ∼5 per cent of the main-sequence phase. We show that with only a modest violation of the Eddington limit, e.g. a factor of ∼10, both the numbers and properties of the majority of the ULXs can be reproduced. One of our conclusions is that if stellar-mass BH binaries account for a significant fraction of ULXs in star-forming galaxies, then the rate of formation of such systems is  ∼3 × 10⁻⁷ yr⁻¹  normalized to a core-collapse supernova rate of 0.01 yr⁻¹.  相似文献   

Oscillation modes of relativistic slender tori   总被引：1，自引：0，他引：1  

O. M. Blaes  P. Arras  P. C. Fragile 《Monthly notices of the Royal Astronomical Society》2006,369(3):1235-1252

Accretion flows with pressure gradients permit the existence of standing waves which may be responsible for observed quasi-periodic oscillations (QPO's) in X-ray binaries. We present a comprehensive treatment of the linear modes of a hydrodynamic, non-self-gravitating, polytropic slender torus, with arbitrary specific angular momentum distribution, orbiting in an arbitrary axisymmetric space–time with reflection symmetry. We discuss the physical nature of the modes, present general analytic expressions and illustrations for those which are low order, and show that they can be excited in numerical simulations of relativistic tori. The mode oscillation spectrum simplifies dramatically for near Keplerian angular momentum distributions, which appear to be generic in global simulations of the magnetorotational instability. We discuss our results in light of observations of high frequency QPO's, and point out the existence of a new pair of modes which can be in an approximate 3:2 ratio for arbitrary black hole spins and angular momentum distributions, provided the torus is radiation pressure dominated. This mode pair consists of the axisymmetric vertical epicyclic mode and the lowest order axisymmetric breathing mode.  相似文献   

The effect of gravitational recoil on black holes forming in a hierarchical universe     

Noam I. Libeskind  Shaun Cole  Carlos S. Frenk  John C. Helly 《Monthly notices of the Royal Astronomical Society》2006,368(3):1381-1391

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Time-dependent, force-free, degenerate electrodynamics     

S. S. Komissarov 《Monthly notices of the Royal Astronomical Society》2002,336(3):759-766

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Iron Kα line profiles and the inner boundary condition of accretion flows     

A. Merloni  A. C. Fabian 《Monthly notices of the Royal Astronomical Society》2003,342(3):951-961

Recent X-ray observations have shown evidence for exceptionally broad and skewed iron Kα emission lines from several accreting black hole systems. The lines are assumed to be due to fluorescence of the accretion disc illuminated by a surrounding corona and require a steep emissivity profile increasing into the innermost radius. This appears to question both standard accretion disc theory and the zero-torque assumption for the inner boundary condition, both of which predict a much less extreme profile. Instead it argues that a torque may be present due to magnetic coupling with matter in the plunging region or even to the spinning black hole itself. Discussion so far has centred on the torque acting on the disc. However, the crucial determinant of the iron line profile is the radial variation of the power radiated in the corona. Here we study the effects of different inner boundary conditions on the coronal emissivity and on the profiles of the observable Fe Kα lines. We argue that in the extreme case where a prominent highly redshifted component of the iron line is detected, requiring a steep emissivity profile in the innermost part and a flatter one outside, energy from the gas plunging into the black hole is being fed directly to the corona.  相似文献   

Studies on the phosphorus requirement and proper calcium/phosphorus ratio in the diet of the black sea bream (Sparus macrocephalus)     

Liu Jingke  Li Maotang  Wang Keling  Wang Xincheng  Liu Jianking 《中国海洋湖沼学报》1993,11(2):130-134

An expriment on the phosphorus requirement and the proper Ca/P ratio in the diet of the black sea bream using the phosphorus gradient method (with casein as basic diet, sodium dihydrogen phosphate as source of phosphorus, and calcium lactate as source of calcium) showed that growth was greatly affected by the diet's phosphorus content and Ca/P ratio. Inadequate phosphorus in the diet resulted in slow growth and poor food conversion ratio (FCR). Analyses of the fish body showed it contained a high level of lipid but a low level of moisture, ash, calcium and phosphorus. The optimal values of phosphorus and Ca/P ratio in the black sea bream diet are 0.68% and 1∶2 respectively. Phosphorus in excess of this optimum value resulted in slow growth or even death. The results of this experiment clearly indicated that phosphorus is the principal mineral additive affecting black sea bream growth. Contribution No. 1972 from the Institute of Oceanology, Academia Sinica.  相似文献