14186187
Accretion Flow along a Dipolar Field: Application to Intermediate Polars
A hydrodynamic formulation for accretion flow channeled by a dipolar magnetic field is constructed using a curvi-linear coordinate system natural to the field structure. We solve the hydrodynamic equations and determine the velocity, density and temperature profiles of the post-shock accretion flow. The results are applied to accretion flows in intermediate polars. We have found that for systems with massive white dwarfs (~ 1 M ⊙ ) the temperature profiles in the flow can differ significantly to those obtained from models in which the accretion column is assumed to be cylindrical.
119332271
Low and High Angular Momentum Accretion Flows in BHCs: Case Study of XTE J1550-564
The 1998 outburst of XTE J1550-564 started with a hard X-ray spike, rising in less than a day and declining after 3-4 days; at the same time, the soft X-ray flux was rising with a longer timescale (~ 10 days). We suggest that the soft and the initial hard X-ray emission are produced by two different components of the accretion flow: a higher angular momentum flow, which forms the disk, and a lower angular momentum flow feeding the hot inner region. Thus, we argue that the onset of the outburst is determined by an increased mass transfer rate from the companion star, but the outburst morphology is also determined by the distribution of specific angular momentum in the accreting matter. In XTE J1550-564, we attribute the initial, impulsive low angular momentum accretion to the breaking down of magnetic confinement by the magnetically active secondary star. We show that a hard X-ray spike is seen at the onset of an outburst in other BHCs.
1734663
Line emission from optically thick relativistic accretion tori
We calculate line emission from relativistic accretion tori around Kerr black holes and investigate how the line profiles depend on the viewing inclination, spin of the central black hole, parameters describing the shape of the tori, and spatial distribution of line emissivity on the torus surface. We also compare the lines with those from thin accretion disks. Our calculations show that lines from tori and lines from thin disks share several common features. In particular, at low and moderate viewing inclination angles they both have asymmetric double-peaked profiles with a tall, sharp blue peak and a shorter red peak which has an extensive red wing. At high viewing inclination angles they both have very broad, asymmetric lines which can be roughly considered as single-peaked. Torus and disk lines may show very different red and blue line wings, but the differences are due to the models for relativistic tori and disks having differing inner boundary radii. Self-eclipse and lensing play some role in shaping the torus lines, but they are effective only at high inclination angles. If inner and outer radii of an accretion torus are the same as those of an accretion disk, their line profiles show substantial differences only when inclination angles are close to 90°, and those differences manifest mostly at the central regions of the lines instead of the wings.
83259
Measuring the Motion of the Black Hole in GRO J1655–40
We report optical spectroscopic observations of the low-mass X-ray binary GRO J1655-40 during outbursts in 1994 August-September and in 1996 June. The spectra show emission and absorption lines from the accretion disk surrounding the X-ray source, which have enabled us to measure the motion of the black hole candidate in this system. It is the first time among black hole candidates that an emission-line radial velocity curve is seen in phase with the expected motion of the primary. The projected radial velocity semiamplitude determined for the primary (KX = 76.2±7.5 km s-1), combined with estimates of the projected radial velocity semiamplitude of the companion star from previous observations (KC=228.2±3.0 km s-2), yields a 95% confidence limit, derived purely from kinematics, of MX > 5.1 M☉ for the mass of the compact object in GRO J1655-40, confirming its black hole nature.
13854637
Ionization structure in accretion shocks with a composite cooling function
ABSTRA C T We have investigated the ionization structure of the post-shock regions of magnetic cataclysmic variables, using an analytic density and temperature structure model in which effects caused by bremsstrahlung and cyclotron cooling are considered. We find that in the majority of the shock-heated region where H- and He-like lines of the heavy elements are emitted, the collisional-ionization and corona-condition approximations are justified. We have calculated the line emissivity and ionization profiles for iron as a function of height within the post-shock flow. For low-mass white dwarfs, line emission takes place near the shock. For high-mass white dwarfs, most of the line emission takes place in regions well below the shock and hence it is less sensitive to the shock temperature. Thus, the line ratios are useful to determine the white dwarf masses for the low-mass white dwarfs, but the method is less reliable when the white dwarfs are massive. Line spectra can, however, be used to map the hydrodynamic structure of the post-shock accretion flow.
14786495
State transitions in LMC X-3
We carried out a multiwavelenght study of the black-hole candidate LMC X-3 with XMM-Newton. The system showed a transition to a low-hard state, in which the X-ray spectrum was well fitted by a simple power law. It then returned to a high-soft state, characterised by a strong disk-blackbody component. The line-of-sight absorption column density is <~ 4 x 10^{20} cm^{-2} consistent with the foreground Galactic absorption. This rules out wind accretion. We argue that, despite LMC X-3 being a high-mass X-ray binary, Roche-lobe overflow is the main mechanism of mass transfer. From UV/optical observations in the low-hard state, we determine that the companion is a slightly evolved B5 star with a mass M ~ 4.5 M_sun. This is indeed consistent with the secondary star being close to filling its Roche lobe.
122037357
A Z2-gauge symmetry in CPT and the Weinberg-Salam model
By means of an approach to the generalized gauge theory on discrete groups, we present a model of GL*GR*Z2 gauge invariance where the Higgs field is a gauge field with respect to the Z2-gauge symmetry, a subgroup of the CPT symmetry. As an example, we reformulate the Weinberg-Salam model.
119041621
Total variation in Hamiltonian formalism and symplectic energy integrators
We present a discrete total variation calculus in Hamiltonian formalism in this paper. Using this discrete variation calculus and generating functions for the flows of Hamiltonian systems, we derive symplectic-energy integrators of any finite order for Hamiltonian systems from a variational perspective. The relationship between the symplectic integrators derived directly from the Hamiltonian systems and the variationally derived symplectic-energy integrators is explored.
122884461
On the composition laws of Beltrami-Liouville theories and 2D quantum gravity☆
Abstract We present the composition laws or cocycle conditions of the Liouville theory and Beltrami-Liouville theory as well as the quantum gravity in two dimensions. We show that for the 2D gravity, their special cases give rise to the composition laws of Polyakov's light-cone action and that of the geometric action of the Virasoro group. By means of the composition laws, we give the gravitational Ward identities and a relation between the actions of the Liouville theory and the topological gravity and find that the principal action of the 2D topological gravity is a coboundary which should obey a cocylce condition in the Liouville complex.
121089433
Symmetric and Asymmetric Anomalies and Effective Lagrangian
The properties of the effective Lagrangian for the low-energy Goldstone-gauge field system constructed from the Chern-Simons topological invariant are further discussed. Both the symmetric anomaly and the asymmetric anomaly are connected with this Lagrangian.
122786546
Field equations, conservation laws in 2D quantum gravity and the Beltrami-KdV-Liouville system
Abstract We present the equations of motion and the conservation laws under various gauges of 2D induced gravity as a kind of the Beltrami-Liouville theory. We generalize the schwarzian derivative and derive its composition law. We also find the relation between the Beltrami-Liouville theory and the KdV system as well as the reccursion relations due to Gel'fand and Dikii based on the properties of the quasiconformal transformations.