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Binary
Kinds of Binary Terms modified by Binary Selected AbstractsCalculated Enthalpies for Dimerisation of Binary, Unsaturated, Main-Group Element Hydrides as a Means to Analyse Their Potential for Multiple BondingEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2003Hans-Jörg Himmel Abstract Herein, the dimerisation of subvalent, binary, main-group element hydrides with the potential for multiple bonding is studied using both hybrid DFT (B3LYP) and ab initio [MP2 and CCSD(T)] methods. The [2+2] cycloaddition is an important and characteristic reaction of derivatives of ethylene. A comparison of dimerisation reactions for several compounds with the potential for multiple bonding should, therefore, shed light on the properties of these species. Our study includes the hydrides E2H2 (E = B, Al, Ga, N P or As), E2H4 (E = C, Si or Ge) and ENH4 (E = B, Al or Ga) and their dimers. Several isomeric forms of the monomers and dimers have to be considered. The trends within a group and a period are established and the factors responsible for them are discussed. It turns out that, generally, the enthalpies for dimerisation increase for heavier homologues, reflecting that the most important factor is the reduced strength of the E,E bonds in the monomers prior to dimerisation and, to some degree, also the reduced ring strain in the cyclic dimers. The exceptions are the dimerisations of B2H2 and Al2H2, both of which lead to the tetrahedral E4H4 species (E = B or Al). Dimerisation of Al2H2 is associated with a smaller enthalpy than that for the dimerisation of B2H2. Comparisons and analyses are made complicated because of the changes in the structures of the isomeric global minima between homologues. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Increasing recyclability of PC, ABS and PMMA: Morphology and fracture behavior of binary and ternary blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Jan Rybnicek Abstract Binary and ternary blends of PC, ABS, and PMMA were studied. The blends were produced from original and recycled materials by melt mixing in a wide range of compositions. Instrumented Charpy impact testing, tensile testing, rheology investigations, and electron microscopy were carried out to determine the relationship between the deformation and fracture behavior, blend composition, morphology, and processing parameters. Resistance against unstable crack propagation was evaluated using the concepts of J -integral and crack-tip-opening displacement (CTOD). The transition from ductile elastic-plastic to brittle-linear elastic fracture behavior was observed in the case of PC/ABS/PMMA blend at 10% of PMMA. Reprocessing had only a slight influence on the deformation and fracture behavior of the recycled blends. The blends produced from recycled materials proved to be competitive with the original pure materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] The Formation of Ordered Nanoholes in Binary, Chemically Similar, Symmetric Diblock Copolymer Blend Films,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 12 2004Yu Xuan Abstract Summary: Binary symmetric diblock copolymer blends, that is, low-molecular-weight poly(styrene- block -methyl methacrylate) (PS- b -PMMA) and high-molecular-weight poly(styrene- block -methacrylate) (PS- b -PMA), self-assemble on silicon substrates to form structures with highly ordered nanoholes in thin films. As a result of the chemically similar structure of the PMA and the PMMA block, the PMMA chain penetrates through the large PMA block that absorbs preferentially on the polar silicon substrate. This results in the formation of nanoholes in the PS continuous matrix. An atomic force microscopy image of the thin film obtained from the blend of low-molecular-weight PS- b -PMMA and high-molecular-weight PS- b -PMA. The regular array of nanoholes in the films surface is clearly visible. [source] Demographic and socio-economic factors associated with dental health among older people in NSWAUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 1 2004Clare Ringland Objective: To investigate the association between oral health status and social, economic and demographic factors in community-dwelling older people in New South Wales (NSW). Methods: Binary and multinomial logistic regression analyses were used to examine the associations between measures of oral health status (edentulous/dentate, and the frequency of toothache or mouth or denture problems in the previous 12 months) and demographic and socio-economic factors using data from the NSW Older People's Health Survey 1999. Results: After adjusting for other factors, being edentulous was associated with being older, having no private dental insurance, being female, leaving school at less than 15 years of age, not being financially comfortable, not being a homeowner, living in a rural area, and being unable to travel alone. Among both dentate and edentulous people, increasing age and being able to travel independently were associated with decreased reporting of toothache, mouth or denture problems; while not being financially comfor table was associated with increased reporting of toothache or mouth or denture problems. The frequency of mouth or denture problems was not found to be independently associated with having private dental insurance nor with holding a health concession card. Conclusions: Among older people in NSW, oral health is associated with a range of demographic and socio-economic factors. The results suggest that better oral health among older people is associated with a capacity to pay out-of-pocket dental expenses rather than with private dental insurance or having access to public-funded dental care. [source] Association Models for Clustered Data with Binary and Continuous ResponsesBIOMETRICS, Issue 1 2010Lanjia Lin Summary We consider analysis of clustered data with mixed bivariate responses, i.e., where each member of the cluster has a binary and a continuous outcome. We propose a new bivariate random effects model that induces associations among the binary outcomes within a cluster, among the continuous outcomes within a cluster, between a binary outcome and a continuous outcome from different subjects within a cluster, as well as the direct association between the binary and continuous outcomes within the same subject. For the ease of interpretations of the regression effects, the marginal model of the binary response probability integrated over the random effects preserves the logistic form and the marginal expectation of the continuous response preserves the linear form. We implement maximum likelihood estimation of our model parameters using standard software such as PROC NLMIXED of SAS. Our simulation study demonstrates the robustness of our method with respect to the misspecification of the regression model as well as the random effects model. We illustrate our methodology by analyzing a developmental toxicity study of ethylene glycol in mice. [source] Volume Chemistry of Hydrogen in Binary and Ternary Metal Hydrides.CHEMINFORM, Issue 16 2005Welf Bronger No abstract is available for this article. [source] Pt2(HSO4)2(SO4)2, the First Binary Sulfate of Platinum.CHEMINFORM, Issue 39 2004Martin Pley Abstract For Abstract see ChemInform Abstract in Full Text. [source] Calculated Enthalpies for Dimerization of Binary, Unsaturated, Main-Group Element Hydrides as a Means to Analyse Their Potential for Multiple Bonding.CHEMINFORM, Issue 31 2003Hans-Joerg Himmel No abstract is available for this article. [source] The Subtle Influence of Binary versus Homoatomic Zintl Ions: The Phenyl-Ligated Trimetallic Cage [Sn2Sb5(ZnPh)2]3,CHEMISTRY - A EUROPEAN JOURNAL, Issue 47 2009Felicitas Lips Dipl.-Chem. Zintlating stuff! The first binary Sn/Sb Zintl anions produced by solution techniques were obtained in [K([2.2.2]crypt)]2[Sn2Sb2],en (en=ethylenediamine) and [K6(NH3)9][Sn3Sb4] upon extraction of K8SnSb4 by en or liquid ammonia. Addition of ZnPh2 to the en/[2.2.2]crypt extract resulted in the formation of a heterotrimetallic complex in [K([2.2.2]crypt)]3[Sn2Sb5(ZnPh)2],en,0.5tol (see scheme). [source] Multivalued and Reversible Logic Gates Implemented with Metallic Nanoparticles and Organic LigandsCHEMPHYSCHEM, Issue 8 2010Javier Cervera Dr. It makes perfect sense: Binary and multivalued XOR gates based on metal nanoparticles linked to electrodes by organic ligands are described. The logic scheme makes use of the Coulomb blockade in the metallic nanoparticles and the electron tunneling in the organic ligands. A reversible logic Feynman gate (see picture) can also be implemented. [source] Optimization of integrated Earth System Model components using Grid-enabled data management and computationCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 2 2007A. R. Price Abstract In this paper, we present the Grid enabled data management system that has been deployed for the Grid ENabled Integrated Earth system model (GENIE) project. The database system is an augmented version of the Geodise Database Toolbox and provides a repository for scripts, binaries and output data in the GENIE framework. By exploiting the functionality available in the Geodise toolboxes we demonstrate how the database can be employed to tune parameters of coupled GENIE Earth System Model components to improve their match with observational data. A Matlab client provides a common environment for the project Virtual Organization and allows the scripting of bespoke tuning studies that can exploit multiple heterogeneous computational resources. We present the results of a number of tuning exercises performed on GENIE model components using multi-dimensional optimization methods. In particular, we find that it is possible to successfully tune models with up to 30 free parameters using Kriging and Genetic Algorithm methods. Copyright © 2006 John Wiley & Sons, Ltd. [source] DECOLONIZING THE PRODUCTION OF GEOGRAPHICAL KNOWLEDGES?GEOGRAFISKA ANNALER SERIES B: HUMAN GEOGRAPHY, Issue 3 2006REFLECTIONS ON RESEARCH WITH INDIGENOUS MUSICIANS ABSTRACT. This paper contributes to debates on decolonizing geography, by reflecting on the ethical and political considerations involved in research on indigenous music in Australia. The research collaboration involved two non-indigenous researchers,an academic geographer and a music educator,engaging with indigenous music and musicians in a number of ways. The paper reflects on these engagements, and draws attention to a series of key binaries and boundaries that were highlighted and unsettled: ,outsider/insider'; ,traditional/contemporary'; ,authenticity/inauthenticity'. It also discusses the politics of publishing and draws attention to the ways in which the objects of our work,in this case a book,influence decisions about representation, subject matter, and interpretations of speaking positions. Rather than seeking validation for attempts to ,speak for' or ,speak to' indigenous musical perspectives, contemporary Aboriginality was understood as a field of intersubjective relations where multiple voices, representations and interventions are made. I discuss some ways in which the authors sought to situate their own musical, and geographical, knowledges in this problematic, and inherently political, research context. [source] New slavery, old binaries: human trafficking and the borders of ,freedom'GLOBAL NETWORKS, Issue 2 2010JULIA O'CONNELL DAVIDSON Abstract This article explores dominant discourse on ,trafficking as modern slavery' in relation to the many legal and social fetters that have historically been and are today imposed upon individuals who are socially imagined as ,free'. It argues that discourse on ,trafficking as modern slavery' revitalizes the liberal understandings of freedom and restriction that have historically allowed vigorous moral condemnation of slavery to coexist with the continued imposition of extensive, forcible restrictions on individuals deemed to be ,free'. In place of efforts to build political alliances between different groups of migrants, as well as between migrants and non-migrants, who share a common interest in transforming existing social and political relations, ,trafficking as modern slavery' discourse inspires and legitimates efforts to divide a small number of ,deserving victims' from the masses that remain ,undeserving' of rights and freedoms. [source] Cities and the ,War on Terror'INTERNATIONAL JOURNAL OF URBAN AND REGIONAL RESEARCH, Issue 2 2006STEPHEN GRAHAM Programmes of organized, political violence have always been legitimized and sustained through complex imaginative geographies. These tend to be characterized by stark binaries of place attachment. This article argues that the discursive construction of the Bush administration's ,war on terror' since September 11th 2001 has been deeply marked by attempts to rework imaginative geographies separating the urban places of the US ,homeland' and those Arab cities purported to be the sources of ,terrorist' threats against US national interests. On the one hand, imaginative geographies of US cities have been reworked to construct them as ,homeland' spaces which must be re-engineered to address supposed imperatives of ,national security'. On the other, Arab cities have been imaginatively constructed as little more than ,terrorist nest' targets to soak up US military firepower. Meanwhile, the article shows how both ,homeland' and ,target' cities are increasingly being treated together as a single, integrated ,battlespace' within post 9/11 US military doctrine and techno-science. The article concludes with a discussion of the central roles of urban imaginative geographies, overlaid by transnational architectures of US military technology, in sustaining the colonial territorial configurations of a hyper-militarized US Empire. [source] No Shades of Gray: The Binary Discourse of George W. Bush and an Echoing PressJOURNAL OF COMMUNICATION, Issue 2 2004Kevin Coe Binary communications represent the world as a place of polar opposites. Such conceptions of reality, although not uncommon in Western thought, take on a heightened importance when political leaders employ them in a concerted, strategic discourse in a mass media environment. With this in mind, this research offers a conception of binary discourse and uses this as a foundation to examine (a) the use of binaries by U.S. President George W. Bush in 15 national addresses, from his inauguration in January 2001 to commencement of the Iraq War in March 2003, and (b) the responses of editorials in 20 leading U.S. newspapers to the president's communications. [source] A theoretical study on the structures and energetics of hypothetical TiM(NCN)3 compounds of the 3d transition metalsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 11 2005Maxence Launay Abstract Quasi-ternary cyanamides and carbodiimides of general formula AB(NCN)3 with A , B have neither been predicted nor synthesized. Thus, hypothetical compounds of that kind containing 3d transition metals were considered (A = Ti, B = Mn, Fe, Co, Ni, Cu) by means of density-functional calculations on 34 structural models, most of which were derived from chemically related phases. After performing structure optimizations based on the local-density approximation, the relative energetic orderings are rationalized in terms of geometrical factors such as molar volumes and polyhedral connections. Total-energy generalized-gradient calculations evidence that the most stable models are enthalpically favored with respect to the elements. Even at ambient temperatures, the ternary phases are predicted as being thermodynamically stable in terms of their Gibbs free formation energies, especially if energetically competing and low-lying binaries (TiC, TiN) can be excluded by a kinetic reaction control. The best models are characterized by low-spin magnetic transition metals found in octahedral coordination, and the TiN6 and MN6 polyhedra either share faces or edges. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 1180,1188, 2005 [source] A systematic study of low-mass X-ray binaries in the M31 globular cluster systemMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2010Mark B. Peacock ABSTRACT We investigate low-mass X-ray binaries (LMXBs) in the M31 globular cluster (GC) system using data from the 2XMMi catalogue. These X-ray data are based on all publicly available XMM,Newton observations of the galaxy. This new survey provides the most complete and homogeneous X-ray survey of M31's GCs to date, covering >80 per cent of the confirmed old clusters in the galaxy. We associate 41 X-ray sources with confirmed old clusters in the recent M31 cluster catalogue of Peacock et al. Comparing these data with previous surveys of M31, it is found that three of these clusters are newly identified, including a bright transient source in the cluster B128. Four additional clusters, that are not detected in these 2XMMi data, have previously been associated with X-ray sources from Chandra or ROSAT observations. Including these clusters, we identify 45 clusters in M31 which are associated with X-ray emission. By considering the latest optical GC catalogues, we identify that three of the previously proposed X-ray clusters are likely to be background galaxies and two have stellar profiles. We consider the properties of LMXB hosting clusters and confirm significant trends between the presence of an LMXB and the metallicity, luminosity and stellar collision rate of a cluster. We consider the relationship between the luminosity and stellar collision rate of a cluster and note that LMXB hosting clusters have higher than average stellar collision rates for their mass. Our findings strongly suggest that the stellar collision rate is the dominant parameter related to the presence of LMXBs. This is consistent with the formation of LMXBs in GCs through dynamical interactions. [source] High-dispersion spectroscopy of two A supergiant systems in the Small Magellanic Cloud with novel propertiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2010R. E. Mennickent ABSTRACT We present the results of a spectroscopic investigation of two novel variable bright blue stars in the SMC, OGLE004336.91-732637.7 (SMC-SC3) and the periodically occulted star OGLE004633.76-731204.3 (SMC-SC4), whose photometric properties were reported by Mennickent et al. (2010). High-resolution spectra in the optical and far-UV show that both objects are actually A + B type binaries. Three spectra of SMC-SC4 show radial velocity variations, consistent with the photometric period of 184.26 d found in Mennickent et al. 2010. The optical spectra of the metallic lines in both systems show combined absorption and emission components that imply that they are formed in a flattened envelope. A comparison of the radial velocity variations in SMC-SC4 and the separation of the V and R emission components in the H, emission profile indicate that this envelope, and probably also the envelope around SMC-SC3, is a circumbinary disc with a characteristic orbital radius some three times the radius of the binary system. The optical spectra of SMC-SC3 and SMC-SC4 show, respectively, He i emission lines and discrete blue absorption components (BACs) in metallic lines. The high excitations of the He i lines in the SMC-SC3 spectrum and the complicated variations of Fe ii emission and absorption components with orbital phase in the spectrum of SMC-SC4 suggests that shocks occur between the winds and various static regions of the stars' corotating binary-disc complexes. We suggest that BACs arise from wind shocks from the A star impacting the circumbinary disc and a stream of former wind-efflux from the B star accreting on to the A star. The latter picture is broadly similar to mass transfer occurring in the more evolved (but less massive) algol (B/A + K) systems, except that we envision transfer occurring in the other direction and not through the inner Lagrangian point. Accordingly, we dub these objects prototype of a small group of Magellanic Cloud wind-interacting A + B binaries. [source] PG 1258+593 and its common proper motion magnetic white dwarf counterpartMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2010J. Girven ABSTRACT We confirm SDSS J130033.48+590407.0 as a common proper motion companion to the well-studied hydrogen-atmosphere (DA) white dwarf PG 1258+593 (GD322). The system lies at a distance of 68 ± 3 pc, where the angular separation of 16.1 ± 0.1 arcsec corresponds to a minimum binary separation of 1091 ± 7 au. SDSS J1300+5904 is a cool (Teff= 6300 ± 300 K) magnetic white dwarf (B, 6 mG). PG 1258+593 is a DA white dwarf with Teff= 14790 ± 77 K and log g= 7.87 ± 0.02. Using the white dwarf mass,radius relation implies the masses of SDSS J1300+5904 and PG 1258+593 are 0.54 ± 0.06 and 0.54 ± 0.01 M,, respectively, and therefore a cooling age difference of 1.67 ± 0.05 Gyr. Adopting main-sequence lifetimes from stellar models, we derive an upper limit of 2.2 M, for the mass of the progenitor of PG 1258+593. A plausible range of initial masses is 1.4,1.8 M, for PG 1258+593 and 2,3 M, for SDSS J1300+5904. Our analysis shows that white dwarf common proper motion binaries can potentially constrain the white dwarf initial mass,final mass relation and the formation mechanism for magnetic white dwarfs. The magnetic field of SDSS J1300+5904 is consistent with an Ap progenitor star. A common envelope origin of the system cannot be excluded, but requires a triple system as progenitor. [source] 3D models of radiatively driven colliding winds in massive O + O star binaries , III.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2010Thermal X-ray emission ABSTRACT The X-ray emission from the wind,wind collision in short-period massive O + O star binaries is investigated. The emission is calculated from 3D hydrodynamical models which incorporate gravity, the driving of the winds, orbital motion of the stars and radiative cooling of the shocked plasma. Changes in the amount of stellar occultation and circumstellar attenuation introduce phase-dependent X-ray variability in systems with circular orbits, while strong variations in the intrinsic emission also occur in systems with eccentric orbits. The X-ray emission in eccentric systems can display strong hysteresis, with the emission softer after periastron than at corresponding orbital phases prior to periastron, reflecting the physical state of the shocked plasma at these times. Our simulated X-ray light curves bear many similarities to observed light curves. In systems with circular orbits the light curves show two minima per orbit, which are identical (although not symmetric) if the winds are identical. The maxima in the light curves are produced near quadrature, with a phase delay introduced due to the aberration and curvature of the wind collision region. Circular systems with unequal winds produce minima of different depths and duration. In systems with eccentric orbits the maxima in the light curves may show a very sharp peak (depending on the orientation of the observer), followed by a precipitous drop due to absorption and/or cooling. We show that the rise to maximum does not necessarily follow a 1/dsep law. Our models further demonstrate that the effective circumstellar column can be highly energy dependent. Therefore, spectral fits which assume energy-independent column(s) are overly simplified and may compromise the interpretation of observed data. To better understand observational analyses of such systems we apply Chandra and Suzaku response files, plus Poisson noise, to the spectra calculated from our simulations and fit these using standard xspec models. We find that the recovered temperatures from two- or three-temperature mekal fits are comparable to those from fits to the emission from real systems with similar stellar and orbital parameters/nature. We also find that when the global abundance is thawed in the spectral fits, subsolar values are exclusively returned, despite the calculations using solar values as input. This highlights the problem of fitting oversimplified models to data, and of course is of wider significance than just the work presented here. Further insight into the nature of the stellar winds and the wind,wind collision region in particular systems will require dedicated hydrodynamical modelling, the results of which will follow in due course. [source] An additional soft X-ray component in the dim low/hard state of black hole binariesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2010C. Y. Chiang ABSTRACT We test the truncated disc models using multiwavelength (optical/ultraviolet/X-ray) data from the 2005 hard state outburst of the black hole Swift J1753.5,0127. This system is both fairly bright and has fairly low interstellar absorption, so gives one of the best data sets to study the weak, cool disc emission in this state. We fit these data using models of an X-ray illuminated disc to constrain the inner disc radius throughout the outburst. Close to the peak, the observed soft X-ray component is consistent with being produced by the inner disc, with its intrinsic emission enhanced in temperature and luminosity by reprocessing of hard X-ray illumination in an overlap region between the disc and corona. This disc emission provides the seed photons for Compton scattering to produce the hard X-ray spectrum, and these hard X-rays also illuminate the outer disc, producing the optical emission by reprocessing. However, the situation is very different as the outburst declines. The optical is probably cyclo-synchrotron radiation, self-generated by the flow, rather than tracing the outer disc. Similarly, limits from reprocessing make it unlikely that the soft X-rays are directly tracing the inner disc radius. Instead they appear to be from a new component. This is seen more clearly in a similarly dim low/hard state spectrum from XTE J1118+480, where the 10 times lower interstellar absorption allows a correspondingly better view of the ultraviolet/extreme ultraviolet (EUV) emission. The very small emitting area implied by the relatively high temperature soft X-ray component is completely inconsistent with the much larger, cooler, ultraviolet component which is well fit by a truncated disc. We speculate on the origin of this component, but its existence as a clearly separate spectral component from the truncated disc in XTE J1118+480 shows that it does not simply trace the inner disc radius, so cannot constrain the truncated disc models. [source] The outburst duration and duty cycle of GRS 1915+105MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2009Patrick Deegan ABSTRACT The extraordinarily long outburst of GRS 1915+105 makes it one of the most remarkable low-mass X-ray binaries (LMXBs). It has been in a state of constant outburst since its discovery in 1992, an eruption which has persisted ,100 times longer than those of more typical LXMBs. The long orbital period of GRS 1915+105 implies that it contains large and massive accretion disc which is able to fuel its extreme outburst. In this paper, we address the longevity of the outburst and quiescence phases of GRS 1915+105 using smooth particle hydrodynamics (SPH) simulations of its accretion disc through many outburst cycles. Our model is set in the two-, framework and includes the effects of the thermoviscous instability, tidal torques, irradiation by central X-rays and wind mass loss. We explore the model parameter space and examine the impact of the various ingredients. We predict that the outburst of GRS 1915+105 should last a minimum of 20 yr and possibly up to ,100 yr if X-ray irradiation is very significant. The predicted recurrence times are of the order of 104 yr, making the X-ray duty cycle a few 0.1 per cent. Such a low duty cycle may mean that GRS 1915+105 is not an anomaly among the more standard LMXBs and that many similar, but quiescent, systems could be present in the Galaxy. [source] Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue , I. A sample of systems with components' masses between 1 and 2 M,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009K. G. He, miniak ABSTRACT We derive the absolute physical and orbital parameters for a sample of 18 detached eclipsing binaries from the All-Sky Automated Survey (ASAS) data base based on the available photometry and our own radial velocity (RV) measurements. The RVs are computed using spectra we collected with the 3.9-m Anglo-Australian Telescope (AAT) and its University College London Echelle Spectrograph (UCLES), and the 1.9-m Radcliffe telescope and its Grating Instrument for Radiation Analysis with a Fibre-Fed Echelle (GIRAFFE) at the South African Astronomical Observatory (SAAO). In order to obtain as precise RVs as possible, most of the systems were observed with an iodine cell available at the AAT/UCLES and/or analysed using the two-dimensional cross-correlation technique (TODCOR). The RVs were measured with TODCOR using synthetic template spectra as references. However, for two objects we used our own approach to the tomographic disentangling of the binary spectra to provide observed template spectra for the RV measurements and to improve the RV precision even more. For one of these binaries, AI Phe, we were able to the obtain an orbital solution with an RV rms of 62 and 24 m s,1 for the primary and secondary, respectively. For this system, the precision in M sin3i is 0.08 per cent. For the analysis, we used the photometry available in the ASAS data base. We combined the RV and light curves using phoebe and jktebop codes to obtain the absolute physical parameters of the systems. Having precise RVs, we were able to reach ,0.2 per cent precision (or better) in masses in several cases but in radii, due to the limited precision of the ASAS photometry, we were able to reach a precision of only 1 per cent in one case and 3,5 per cent in a few more cases. For the majority of our objects, the orbital and physical analysis is presented for the first time. [source] Jets from black hole X-ray binaries: testing, refining and extending empirical models for the coupling to X-raysMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2009R. P. Fender ABSTRACT In this paper we study the relation of radio emission to X-ray spectral and variability properties for a large sample of black hole X-ray binary systems. This is done to test, refine and extend , notably into the timing properties , the previously published ,unified model' for the coupling of accretion and ejection in such sources. In 14 outbursts from 11 different sources we find that in every case the peak radio flux, on occasion directly resolved into discrete relativistic ejections, is associated with the bright hard to soft state transition near the peak of the outburst. We also note the association of the radio flaring with periods of X-ray flaring during this transition in most, but not all, of the systems. In the soft state, radio emission is in nearly all cases either undetectable or optically thin, consistent with the suppression of the core jet in these states and ,relic' radio emission from interactions of previously ejected material and the ambient medium. However, these data cannot rule out an intermittent, optically thin, jet in the soft state. In attempting to associate X-ray timing properties with the ejection events we find a close, but not exact, correspondence between phases of very low integrated X-ray variability and such ejections. In fact the data suggest that there is not a perfect one-to-one correspondence between the radio, X-ray spectral or X-ray timing properties, suggesting that they may be linked simply as symptoms of the underlying state change and not causally to one another. We further study the sparse data on the reactivation of the jet during the transition back to the hard state in decay phase of outbursts, and find marginal evidence for this in one case only. In summary we find no strong evidence against the originally proposed model, confirming and extending some aspects of it with a much larger sample, but note that several aspects remain poorly tested. [source] Delayed X-ray emission from fallback in compact-object mergersMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2009Elena M. Rossi ABSTRACT When double neutron star or neutron star,black hole binaries merge, the final remnant may comprise a central solar-mass black hole surrounded by a ,0.01,0.1 M, torus. The subsequent evolution of this disc may be responsible for short ,-ray bursts (SGRBs). A comparable amount of mass is ejected into eccentric orbits and will eventually fallback to the merger site after ,0.01 s. In this paper, we investigate analytically the fate of the fallback matter, which may provide a luminous signal long after the disc is exhausted. We find that matter in the eccentric tail returns at a super-Eddington rate and eventually (,0.1 s) is unable to cool via neutrino emission and accrete all the way to the black hole. Therefore, contrary to previous claims, our analysis suggests that fallback matter is not an efficient source of late-time accretion power and unlikely to cause the late-flaring activity observed in SGRB afterglows. The fallback matter rather forms a radiation-driven wind or a bound atmosphere. In both the cases, the emitting plasma is very opaque and photons are released with a degraded energy in the X-ray band. We therefore suggest that compact binary mergers could be followed by an ,X-ray renaissance', as late as several days to weeks after the merger. This might be observed by the next generation of X-ray detectors. [source] Properties of analytic transit light-curve modelsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008András Pál ABSTRACT In this paper, a set of analytic formulae is presented with which the partial derivatives of the flux obscuration function can be evaluated , for planetary transits and eclipsing binaries , under the assumption of quadratic limb darkening. The knowledge of these partial derivatives is crucial for many of the data modelling algorithms and estimates of the light-curve variations directly from the changes in the orbital elements. These derivatives can also be utilized to speed up some of the fitting methods. A gain of ,8 in computing time can be achieved in the implementation of the Levenberg,Marquardt algorithm, relative to using numerical derivatives. [source] The tightening of wide binaries in dSph galaxies through dynamical friction as a test of the dark matter hypothesisMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2008X. Hernandez ABSTRACT We estimate the time-scales for orbital decay of wide binaries embedded within dark matter haloes, due to dynamical friction against the dark matter particles. We derive analytical scalings for this decay and calibrate and test them through the extensive use of N -body simulations, which accurately confirm the predicted temporal evolution. For density and velocity dispersion parameters as inferred for the dark matter haloes of local dSph galaxies, we show that the decay time-scales become shorter than the ages of the dSph stellar populations for binary stars composed of 1 M, stars, for initial separations larger than 0.1 pc. Such wide binaries are conspicuous and have been well measured in the solar neighbourhood. The prediction of the dark matter hypothesis is that they should now be absent from stellar populations embedded within low velocity dispersion, high-density dark mater haloes, as currently inferred for the local dSph galaxies, having since evolved into tighter binaries. Relevant empirical determinations of this will become technically feasible in the near future, and could provide evidence to discriminate between dark matter particle haloes or modified gravitational theories, to account for the high dispersion velocities measured for stars in local dSph galaxies. [source] Spatial distribution of luminous X-ray binaries in spiral galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008Zhao-yu Zuo ABSTRACT We have modelled the spatial distribution of luminous X-ray binaries (XRBs) in spiral galaxies that are like the Milky Way using an evolutionary population synthesis code. In agreement with previous theoretical expectations and observations, we find that both high- and low-mass XRBs show clear concentrations towards the galactic plane and bulge. We also compare XRB distributions under the galactic potential with a dark matter halo and the modified Newtonian dynamics potential, and we suggest that the difference may serve as potential evidence to discriminate between these two types of model. [source] Spectroscopic and photometric observations of the selected Algol-type binaries , II.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008V2080 Cygni, V2365 Ophiuchi ABSTRACT This paper is the second in the planned series of investigations. We present new radial velocities and photometric observations of V2080 Cyg and V2365 Oph. New UBV photometric data and radial velocities were analysed for the systems' parameters. While V2080 Cyg consists of two nearly equal F-type main-sequence stars, V2365 Oph has two different components, namely an early A-type primary and a G-type secondary star. New ephemerides are calculated for both systems. The masses of the component stars have been derived as 1.19 ± 0.02 and 1.16 ± 0.02 M, for V2080 Cyg and 1.97 ± 0.02 and 1.06 ± 0.01 M, for V2365 Oph. The effective temperatures and reddening of the systems have been estimated from Johnson wide-band UBV photometric calibrations. The radii have been measured by simultaneous fitting the UBV light curves using Wilson,Devinney code and are 1.60 ± 0.01 R, for both components of V2080 Cyg and 2.19 ± 0.01 and 0.934 ± 0.004 R, for V2365 Oph. The absolute parameters of the stars in both systems lie within the same ranges in the mass,radius, mass,effective temperature, mass,luminosity and luminosity,effective temperature planes as in detached Algol systems. A comparison between the properties of the systems of interest and the predictions of theoretical evolutionary models is undertaken in the log g,logTeff, log R, log M and radius,log age diagrams. The model predictions match the measured properties of V2080 Cyg for an age of about 5.6 Gyr and a ,solar' metal abundance (Z= 0.019), indicating the components near the end of their core hydrogen-burning phases. However, the position of the components of V2365 Oph on the Hertzsprung,Russell (HR) diagram is best reproduced with evolutionary models for somewhat metal-deficient (Z= 0.004) stars. We found an age of about 700 Myr, with the primary component slightly evolved off the zero-age main-sequence and the secondary one still very close to it. From the basic stellar parameters we have also redetermined the distances to V2080 Cyg and V2365 Oph as 78 ± 1 and 251 ± 8 pc, which are in agreement with, and more accurate than, Hipparcos values. The observations show that at least one of the components of V2365 Oph is an intrinsic variable with a period and peak-to-peak amplitude of 0.07 d and 0.05 mag, respectively. In accordance with its position in the HR diagram, the primary component should be considered as a , Scuti star and it is believed to be the variable star in the system. [source] Post-common-envelope binaries from SDSS , I. 101 white dwarf main-sequence binaries with multiple Sloan Digital Sky Survey spectroscopyMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007A. Rebassa-Mansergas ABSTRACT We present a detailed analysis of 101 white dwarf main-sequence binaries (WDMS) from the Sloan Digital Sky Survey (SDSS) for which multiple SDSS spectra are available. We detect significant radial velocity variations in 18 WDMS, identifying them as post-common-envelope binaries (PCEBs) or strong PCEB candidates. Strict upper limits to the orbital periods are calculated, ranging from 0.43 to 7880 d. Given the sparse temporal sampling and relatively low spectral resolution of the SDSS spectra, our results imply a PCEB fraction of ,15 per cent among the WDMS in the SDSS data base. Using a spectral decomposition/fitting technique we determined the white dwarf effective temperatures and surface gravities, masses and secondary star spectral types for all WDMS in our sample. Two independent distance estimates are obtained from the flux-scaling factors between the WDMS spectra, and the white dwarf models and main-sequence star templates, respectively. Approximately one-third of the systems in our sample show a significant discrepancy between the two distance estimates. In the majority of discrepant cases, the distance estimate based on the secondary star is too large. A possible explanation for this behaviour is that the secondary star spectral types that we determined from the SDSS spectra are systematically too early by one to two spectral classes. This behaviour could be explained by stellar activity, if covering a significant fraction of the star by cool dark spots will raise the temperature of the interspot regions. Finally, we discuss the selection effects of the WDMS sample provided by the SDSS project. [source] | ||||||||||||||||||||||||||||||||||