12255724
High-resolution optical and infrared spectroscopic observations of Cir X-1
We present new optical and infrared (IR) observations of Cir X-1 taken near apastron. Both sets of spectra show asymmetric emission lines. Archival optical observations show that an asymmetric Ha emission line has been in evidence for the past 20 years, although the shape of the line has changed significantly. We present an eccentric (e , 0:7–0:9 low-mass binary model, where the system consists of a neutron star orbiting around a (sub)giant companion star of 3–5 M(. We suggest that the broad components of the emission lines arise in a highvelocity, optically thick flow near the neutron star, while the narrow components of the optical and the IR lines arise near the companion star and a heated ejecta shell surrounding the binary respectively. In this model, the velocity of the narrow component reflects the space velocity of the binary; the implied radial velocity (1430 km s after correcting for Galactic rotation) is the highest velocity known for an X-ray binary. Key words: binaries: spectroscopic – stars: individual: Cir X-1 – X-rays: stars. 1 I N T RO D U C T I O N Cir X-1 is one of the most puzzling X-ray binaries known. Like the peculiar systems SS 433 and Cyg X-3, it cannot easily be classified into any of the major categories of X-ray binaries. Indeed, there is even doubt as to whether it is a high-mass X-ray binary (HMXB) or a low-mass X-ray binary (LMXB). Since its discovery in the early 1970s, Cir X-1 has been studied intensively at X-ray wavelengths. The X-ray properties of Cir X-1 were found to differ dramatically each time it was observed (see, e.g., Kaluzienski et al. 1976; Tennant 1988; Tsunemi et al. 1989; Shirey et al. 1996). Periodic modulation of the X-ray flux was found at a period of 16.6 d (Kaluzienski et al. 1976). A radio counterpart was detected (Clark, Parkinson & Caswell 1975), and was found to flare at the same period as the X-ray modulation (Haynes et al. 1978). These flares were initially detected at peak flux levels of .1 Jy; since the 1970s, the flux of the source has decreased dramatically, and it has only occasionally been detected above 50 mJy (Stewart et al. 1991). This radio source is located 25 arcmin from the centre of the supernova remnant G 321.920.3, and is apparently connected to the remnant by a radio nebula (Haynes et al. 1986). Stewart et al. (1993) have imaged arcmin-scale collimated structures within the surrounding nebula, suggesting an outflow from the X-ray binary. Fender et al. (1998) have imaged an arcsec-scale asymmetric jet aligned with these larger structures, raising the possibility that the outflow from the system is relativistic. Recently, Case & Bhattacharya (1998) have revised the estimated distance to G 321.920.3 (and hence to Cir X-1, assuming that they are associated) to 5.5 kpc, which is substantially smaller than the original suggested distance to Cir X-1 of 10 kpc (Goss & Mebold 1977). The discovery of Type I X-ray bursts (Tennant, Fabian & Shafer 1986b) suggests that the compact object is probably a weakly magnetized neutron star. The close association of Cir X-1 with the supernova remnant suggests that the system may be a young (,105 yr old) runaway system from a supernova explosion (Stewart et al. 1993). The optical counterpart to Cir X-1 was identified as a highly reddened star with strong Ha emission (Whelan et al. 1977). This object was later shown to consist of three stars within a radius of 1.5 arcsec, the southernmost of which is the true counterpart (Moneti 1992; Duncan, Stewart & Haynes 1993). The long orbital period and periodic X-ray activity suggested a high-mass system in an eccentric orbit (Murdin et al. 1980); however, the variability of the optical emission, the faintness of the optical counterpart, and several of its X-ray characteristics suggest that the companion is a low-mass star. The lack of spectroscopic studies in the optical band means that most of the fundamental orbital parameters of Cir X-1 have not been determined. Moreover, Cir X-1 shows very different properties q 1999 RAS E-mail: hmj@aaoepp.aao.gov.au 416 H. M. Johnston, R. Fender and K. Wu from time to time. This make it difficult to construct a coherent picture for the system from observations of different wavelengths at different epochs. Here we present new spectroscopic observations of Cir X-1, and use these, together with analysis of archival observations of the system, to suggest a more coherent model for the system. 2 O B S E RVAT I O N S A N D DATA R E D U C T I O N 2.1 New optical observations Cir X-1 was observed on 1997 June 4 using the 3.9-m AngloAustralian Telescope (AAT). The mean orbital phase of the observation was 0.51, calculated according the ephemeris of Stewart et al. (1991). The RGO Spectrograph was used in combination with the TEK 1k CCD in the 82-cm camera and a grating of 270 groove mm in first order, resulting in a dispersion of ,1:08 A pixel21 over a wavelength range 6060–7165 A. The spatial scale was 0.25 arcsec pixel; the spectral resolution, measured from the arc lines, was 5.4 A. A 1.5-arcsec-wide slit was used, oriented north–south so that both Cir X-1 and star 2 of Moneti (1992) were in the slit. The atmospheric seeing was about 1 arcsec. Five 1800-s integrations were taken, interspersed with CuAr arc-lamp exposures, before cloud prevented the acquisition of any more data. The bias and pixel-to-pixel gain variations were removed from each exposure using standard procedures in iraf. Cosmic rays were removed using the method of Croke (1995) to compare adjacent frames. Because of the presence of the nearby confusing star (Moneti’s star 2), special care needed to be taken to measure the flux from our object. At every position along the dispersion direction, we fit two Gaussian profiles, with fixed widths FWHM  5:6 pixels and separation (6 pixels), to the skysubtracted frames. The amplitude of these Gaussians was used as the estimate of the flux from Cir X-1 and star 2 at each wavelength. We then determined the wavelength calibration using the CuAr arc lamp exposures. We fitted a low-order polynomial to the arc line wavelengths as a function of pixel number: the rms scatter of the fits was ,1=4 of a pixel. A rough flux-calibration was performed by comparing with the spectrum of the observed flux standard LTT 4364 although, since the night was nonphotometric, this flux calibration should be considered only approximate. 2.2 Infrared observations K-band spectroscopy of Cir X-1 was obtained using the Cryogenic Array Spectrometer/Imager (CASPIR) on the ANU 2.3-m telescope at Siding Spring Observatory on the night of 1997 June 20. The K grism was used with the SBRC 256 256 InSb array, giving a dispersion of 21.5 A pixel over a wavelength range of 1.94–2.49mm. The spatial scale was 0.5 arcsec pixel. A 5-arcsec slit was used, oriented east–west: note that this means that Moneti’s stars 2 and 3 both contributed light in our spectrum. The telescope was nodded by ^12 arcsec along the slit to provide sky frames at the same position as the object. Argon lamp spectra were taken to perform wavelength calibration, and two nearby bright stars (BS 5699 and 5712) were observed in order to remove atmospheric spectral features and perform flux calibration. Standard data reduction procedures were followed, using the local caspir package running in iraf. Bias and dark frames were used to linearize all frames, the sky background was subtracted from the object frames, and pixel-to-pixel variations were corrected. The chip distortion was corrected in order to align the dispersion and spatial directions along rows and columns of the chip; the sky background was then subtracted and spectra extracted. A low-order polynomial was fitted to the argon lines, and these calibrations applied to the object spectra. Flux calibration was achieved by dividing the observed spectra by the spectrum of a nearby mid-G-type star and then multiplying by a model for the absolute flux distribution of the calibrator. Residual terrestrial atmospheric features were then corrected using an early-type star.
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.
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.
18756154
Formation of optical lines in black-hole binaries
The HI Balmer emission lines of black-hole binaries show double-peaked profiles during the high-soft state and the quiescent state. In the high-soft state the profiles are asymmetric with a stronger red peak, but the profiles are symmetric in the quiescent state. We suggest that in the high-soft state the emission lines originate from the temperature-inversion layer caused by irradiative heating of an optically thick accretion disk. Irradiative heating also causes the formation of a disk wind, which mildly absorbs the blue peak of the lines. The double-peaked lines seen in the quiescent state arise from an optically thin disk. In the absence of a disk wind, the lines are unabsorbed and so the symmetry of the line profiles is preserved.
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.
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.
14150373
Axial anomaly in lattice abelian gauge theory in arbitrary dimensions
Abstract The axial anomaly of lattice abelian gauge theory on a hyper-cubic regular lattice in arbitrary even dimensions is investigated by applying the method of exterior differential calculus. The topological invariance, gauge invariance and locality of the axial anomaly determine the explicit form of the topological part. The anomaly is obtained up to a multiplicative constant for finite lattice spacing and can be interpreted as the Chern character of the abelian lattice gauge theory.
16685414
Universal R-matrix Of The Super Yangian Double DY(gl(1|1))
Based on Drinfel ′ d realization of super Yangian Double DY (gl(1|1)), its pairing relations and universal R-matrix are given. By taking evaluation representation of universal R-matrix, another realization L ± (u) of DY (gl(1|1)) is obtained. These two realizations of DY (gl(1|1)) are related by the supersymmetric extension of Ding-Frenkel map. Yangian algebra was introduced by Drinfel ′ d[1, 2]. The quantum double of Yangian consists of Yangian itself and its dual with opposite comultiplication. There are three methods to define the Yangian and Yangian double: Drinfel ′ d-Jmbo [1, 3], Drinfel ′ d new realization [2] and RS approach [5] (or FRT approach [4] in the case of without center extension). The explicit isomorphism between Drinfel ′ d new realization and RS realization of Yangian double can be established through Gauss decomposition, the similar method used by Ding and Frenkel in the discussions of quantum Affine algebra. [6]. The property of Yangian double, such as quasi-triangular properties and equivalence of Drinfel ′ d and RS realization was studied well in some papers [7, 8, 9]. Although the Drinfel ′ d realization of super Yangian double [10, 11] was constructed by means of RS method and Gauss decomposition, the quasi-triangular property, such as universal R-matrix of super Yangian double has not been studied yet. In this paper, we find the Hopf pairing relations between super Yangian Y (gl(1|1)) and its dual, then construct the universal R-matrix of DY (gl(1|1)). By taking evaluation representation, we get the FRT realization of DY (gl(1|1)). Super Yangian double DY (gl(1|1)) is the Hopf algebra generated by elements
16329749
Tau function and Hirota bilinear equations for the extended bigraded Toda hierarchy
In this paper, we generalize the Sato theory to the extended bigraded Toda hierarchy. We revise the definition of the Lax equations, give the Sato equations, wave operators, Hirota bilinear identities, and show the existence of tau function τ(t). Meanwhile, we prove the validity of its Fay-like identities and Hirota bilinear equations (HBEs) in terms of vertex operators whose coefficients take values in the algebra of differential operators. In contrast to HBEs of the usual integrable system, the current HBEs are equations of the product of operators involving e∂x and τ(t).
16106369
The Euler–Lagrange Cohomology and General Volume-Preserving Systems
We briefly introduce the concept of Euler–Lagrange cohomology groups on a symplectic manifold (ℳ2n, ω) and systematically present the general form of volume-preserving equations on the manifold from the cohomological point of view. It is shown that for every volume-preserving flow generated by these equations there is an important two-form that plays the analog role with the Hamiltonian in the Hamilton mechanics. In addition, the ordinary canonical equations with Hamiltonian H are included as a special case with the two-form . The other volume preserving systems on (ℳ2n, ω) are studied. The relations between our approach and Feng–Shang's volume-preserving systems as well as the Nambu mechanics are also explored.
5363796
DEX: Increasing the Capability of Scientific Data Analysis Pipelines by Using Efficient Bitmap Indices to Accelerate Scientific Visualization
We describe a new approach to scalable data analysis that enables scientists to manage the explosion in size and complexity of scientific data produced by experiments and simulations. Our approach uses a novel combination of efficient query technology and visualization infrastructure. The combination of bit map indexing, which is a data management technology that accelerates queries on large scientific datasets, with a visualization pipeline for generating images of abstract data results in a tool suitable for use by scientists in fields where data size and complexity poses a barrier to efficient analysis. Our architecture and implementation, which we call DEX (short for dexterous data explorer), directly addresses the problem of ''too much data'' by focusing analysis on data deemed to be ''scientifically interesting'' via a user-specified selection criteria. The architectural concepts and implementation are applicable to wide variety of scientific data analysis and visualization applications. This paper presents an architectural overview of the system along with an analysis showing substantial performance over traditional visualization pipelines. While performance gains are a significant result, even more important is the new functionality not present in any visualization analysis software--namely the ability to perform interactive, multi-dimensional queries to refine regions of interest that aremore » later used as input to analysis or visualization.« less