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.
8381735
Accretion in dipole magnetic fields: flow structure and X-ray emission of accreting white dwarfs
Field-channelled accretion flows occur in a variety of astrophysical objects, including T Tauri stars, magnetic cataclysmic variables and X-ray pulsars. We consider a curvilinear coordinate system and derive a general hydrodynamic formulation for accretion onto stellar objects confined by a stellar dipole magnetic field. The hydrodynamic equations are solved to determine the velocity, density and temperature profiles of the flow. We use accreting magnetic white-dwarf stars as an illustrative example of astrophysical applications. Our calculations show that the compressional heating due to the field geometry is as important as radiative cooling and gravity in determining the structure of the post-shock flow in accreting white-dwarf stars. The generalisation of the formulation to accretion flows channelled by higher-order fields and the applications to other astrophysical systems are discussed.
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.
119085416
The First Chandra Field
Before the official first-light images, the Chandra X-ray Observatory obtained an X-ray image of the field to which its focal plane was first exposed. We describe this historic observation and report our study of the first Chandra field. Chandra's Advanced CCD Imaging Spectrometer (ACIS) detected 15 X-ray sources, the brightest being dubbed ''Leon X-1'' to honor the Chandra Telescope Scientist, Leon Van Speybroeck. Based upon our analysis of the X-ray data and spectroscopy at the European Southern Observatory (ESO; La Silla, Chile), we find that Leon X-1 is a Type-1 (unobscured) active galactic nucleus (AGN) at a redshift z = 0.3207. Leon X-1 exhibits strong Fe II emission and a broad-line Balmer decrement that is unusually flat for an AGN. Within the context of the Eigenvector-1 correlation space, these properties suggest that Leon X-1 may be a massive ({ge} 10{sup 9} M{sub {circle_dot}}) black hole, accreting at a rate approaching its Eddington limit.
2849596
Relativistic reflection X-ray spectra of accretion disks
We have calculated the relativistic re fl ection component of the X-ray spectra of accretion disks in active galactic nuclei (AGN). Our calculations have shown that the spectra can be signi fi cantly modi fi ed by the motion of the accretion fl ow, and the gravity and rotation of the central black hole. The absorption edges in the spectra suffer severe energy shifts and smearing, and the degree of distortion depends on the system parameters, in particular, the inner radius of the accretion disk and the disk viewing inclination angles. The effects are signi fi cant. Fluorescent X-ray emission lines from the inner accretion disk could be a powerful diagnostic of space-time distortion and dynamical relativistic effects near the event horizons of accreting black holes. However, improper treatment of the re fl ection component in fi tting the X-ray continuum could give rise to spurious line-like features. These features mimic the true fl uorescent emission lines and may mask their relativistic signatures. Fully relativistic models for re fl ection continua together with the emission lines are needed in order to extract black-hole parameters from the AGN X-ray spectra.
59931318
Properties of discrete X-ray sources in the starburst spiral galaxy M 83
We have identified 127 discrete sources in a Chandra ACIS observation of M83, with a detection limit of approximate to3 x 10(36) erg s(-1) in the 0.3-8.0 keV band. We discuss the individual X-ray spectral and time-variability properties of approximate to20 bright sources with luminosities greater than or similar to10(38) erg s(-1), and the statistical properties of the whole sample. About one third of the bright sources show X-ray spectra with a blackbody component at temperatures less than or similar to1 keV, plus a powerlaw component with Gamma approximate to 2.5, typical of X-ray binaries in a soft state; another third have powerlaw spectra with Gamma approximate to 1.5, consistent with X-ray binaries in a hard state. Two bright sources show emission lines on a hard powerlaw continuum, and are probably X-ray binaries surrounded by a photo-ionized nebula or stellar wind. Among the other bright sources, we also identified two supernova remnant candidates, with optically-thin thermal plasma spectra at temperatures similar to0.5 keV. The two brightest supersoft sources have blackbody temperatures kT approximate to 70 eV and luminosities similar to10(38) erg s(-1). Two candidate X-ray pulsars are detected with periods approximate to200 s. One X-ray source corresponds to the core of a background FRII radio galaxy. The discrete sources can be divided into three groups, based on their spatial, color and luminosity distributions. The first group comprises supersoft sources with no detected emission above 1 keV and blackbody spectra at temperatures <100 eV. The second group consists of soft sources with little or no detected emission above 2 keV. They are strongly correlated with H alpha emission in the spiral arms and starburst nucleus, tracing a young population. Their relative abundance depends on the current level of star-forming activity in the galaxy. Most of them are likely to be supernova remnants. The sources in the third group are mostly X-ray binaries, reaching higher X-ray luminosities than sources in the other two groups. Being a mixture of old low-mass and young high-mass systems, the whole group appears to be of intermediate age when correlated with the H alpha emission. The color-color diagrams allow us to distinguish between sources in a soft and hard state.
124321395
ALGEBRAIC APPROACH TO GAUGE-THEORY AND ITS NONCOMMUTATIVE EXTENSION
We propose an alternative algebraic construction of the connection theory on the fiber bundle, and find its non-commutative extension, i.e., the connection theory based on guantum groups. In this construction, the Yang-Baxter equation arises as the exchange relations of connections and a deformed trace of quantum groups is introduced to build up the characteristic classes.
124269485
CHERN-SIMONS FORM IN STRING FIELD THEORY
117147252
THE STANDARD MODEL WITH HIGGS AS GAUGE FIELD ON FOURTH HOMOTOPY GROUP
Based upon a fundamental principle, the generalized gauge principle, we construct a general model with G(L) x G(R)' x Z(2) gauge symmetry, where Z(2) = pi(4)(G(L)) is the fourth homotopy group of the gauge group G(L), by means of the non-commutative differential geometry and reformulating the standard model with the Higgs field being a gauge field on the fourth homotopy group of their gauge groups. We show that in this approach not only the Higgs held is automatically introduced on an equal footing with ordinary Yang-Mills gauge potentials and there are no extra constraints among the parameters at the tree level but also most importantly the models survive quantum corrections.
121705126
Real weight b-c systems and conformal field theory in higher genus
Abstract We define bases for differentials with real weight λ on higher genus Riemann surfaces and the corresponding b - c systems. We generalize them by defining real weight bases and b - c systems describing spin field or vertex insertions at specified points of the Riemann surface. We use this formalism to calculate various kinds of correlation functions of λ-spin fields, for rational λ. We also compute the basic correlation functions of chiral vertex insertions in minimal models.
14603217
Topological obstruction in block-spin transformations
Abstract Block-spin transformations from a fine lattice to a coarse one are shown to give rise to a one-to-one correspondence between the zero-modes of the Ginsparg-Wilson Dirac operator on the fine lattice and those on the coarse lattice. The index is then preserved under the blocking process. Such a one-to-one correspondence is violated and the block-spin transformation becomes necessarily ill-defined when the absolute value of the index is larger than 2 rN , where N is the number of the sites on the coarse lattice and r is the dimension of the gauge group representation of the fermion variables.