729 research outputs found

    Q-phonon description of low lying 1^- two-phonon states in spherical nuclei

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    The properties of 1^-_1 two-phonon states and the characteristics of E1 transition probabilities between low-lying collective states in spherical nuclei are analysed within the Q-phonon approach to the description of collective states. Several relations between observables are obtained. Microscopic calculations of the E1 0^+_1 -> 1^-_1 transition matrix elements are performed on the basis of the RPA. A satisfactory description of the experimental data is obtained.Comment: 16 pages, 2 figures, 9 table

    Vela X-1 as a laboratory for accretion in High-Mass X-ray Binaries

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    Vela X-1 is an eclipsing high mass X-ray binary (HMXB) consisting of a 283s accreting X-ray pulsar in a close orbit of 8.964 days around the B0.5Ib supergiant HD77581 at a distance of just 2.4 kpc. The system is considered a prototype of wind-accreting HMXB and it has been used as a baseline in different theoretical or modelling studies. We discuss the observational properties of the system and the use of the observational data as laboratory to test recent developments in modelling the accretion process in High-Mass X-ray Binaries (e.g., Sander et al. 2018; El Mellah et al. 2018), which range from detailed descriptions of the wind acceleration to modelling of the structure of the flow of matter close to the neutron star and its variations.Comment: 4 pages, 2 figures, proceedings of the 12th INTEGRAL conference "INTEGRAL looks AHEAD to Multimessenger astronomy" in Geneva (Switzerland) on 11-15 February 201

    Long term variability of Cygnus X-1: VII. Orbital variability of the focussed wind in Cyg X-1 / HDE 226868 system

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    Binary systems with an accreting compact object are a unique chance to investigate the strong, clumpy, line-driven winds of early type supergiants by using the compact object's X-rays to probe the wind structure. We analyze the two-component wind of HDE 226868, the O9.7Iab giant companion of the black hole Cyg X-1 using 4.77 Ms of RXTE observations of the system taken over the course of 16 years. Absorption changes strongly over the 5.6 d binary orbit, but also shows a large scatter at a given orbital phase, especially at superior conjunction. The orbital variability is most prominent when the black hole is in the hard X-ray state. Our data are poorer for the intermediate and soft state, but show signs for orbital variability of the absorption column in the intermediate state. We quantitatively compare the data in the hard state to a toy model of a focussed Castor-Abbott-Klein-wind: as it does not incorporate clumping, the model does not describe the observations well. A qualitative comparison to a simplified simulation of clumpy winds with spherical clumps shows good agreement in the distribution of the equivalent hydrogen column density for models with a porosity length on the order of the stellar radius at inferior conjunction; we conjecture that the deviations between data and model at superior conjunction could be either due to lack of a focussed wind component in the model or a more complicated clump structure.Comment: proposed for acceptance in A&A, 11 pages, 11 figures (two in appendix

    Morphological Criteria for Diagnosis of Pulmonary Lesions of Lungs in Tumors Based on Resection Material

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    Morphological criteria of diagnosis of dust lesions of lungs in tumors on resectionmaterial are considered in the article. It is shown that the complex application of various research methods allows the identification of dust particles in the lung and lymph node tissues, and contributes to the improvement of the diagnosis of dust lesions of the respiratory system. Morphological characteristics of bauxite pneumoconiosis in primary lung cancer on resection material are presented

    Diffusion spin echo decay by pulsed magnetic field gradient NMR and some structure features in blockcopolymer solutions

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    Blockcopolymer solutions were investigated by pulsed field gradient NMR. Nonexponential diffusion decay of solvent molecules and the dependence of it's shape on time of observation uere found out. These features (unusual for solvent molecules) were explained on assumption of the solution heterogeneous structure. Consideration, performed, allow us to estimate the linear dimensions of the heterogeneities, which for concentrated systems occured to be near 10000 A. © 1985 Springer-Verlag

    Population of isomers in decay of the giant dipole resonance

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    The value of an isomeric ratio (IR) in N=81 isotones (137^{137}Ba, 139^{139}Ce, 141^{141}Nd and 143^{143}Sm) is studied by means of the (γ,n)\gamma, n) reaction. This quantity measures a probability to populate the isomeric state in respect to the ground state population. In (γ,n)\gamma, n) reactions, the giant dipole resonance (GDR) is excited and after its decay by a neutron emission, the nucleus has an excitation energy of a few MeV. The forthcoming γ\gamma decay by direct or cascade transitions deexcites the nucleus into an isomeric or ground state. It has been observed experimentally that the IR for 137^{137}Ba and 139 ^{139}Ce equals about 0.13 while in two heavier isotones it is even less than half the size. To explain this effect, the structure of the excited states in the energy region up to 6.5 MeV has been calculated within the Quasiparticle Phonon Model. Many states are found connected to the ground and isomeric states by E1E1, E2E2 and M1M1 transitions. The single-particle component of the wave function is responsible for the large values of the transitions. The calculated value of the isomeric ratio is in very good agreement with the experimental data for all isotones. A slightly different value of maximum energy with which the nuclei rest after neutron decay of the GDR is responsible for the reported effect of the A-dependence of the IR.Comment: 16 pages, 4 Fig

    LABORATORY MEASUREMENTS OF THE K-SHELL TRANSITION ENERGIES IN L-SHELL IONS OF SI AND S

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    We have measured the energies of the strongest 1s–2ℓ (ℓ = s, p) transitions in He- through Ne-like silicon and sulfur ions to an accuracy of <1 eV using the Lawrence Livermore National Laboratory's electron beam ion traps, EBIT-I and SuperEBIT, and the NASA/GSFC EBIT Calorimeter Spectrometer (ECS). We identify and measure the energies of 18 and 21 X-ray features from silicon and sulfur, respectively. The results are compared to new Flexible Atomic Code calculations and to semi-relativistic Hartree–Fock calculations by Palmeri et al. (2008). These results will be especially useful for wind diagnostics in high-mass X-ray binaries, such as Vela X-1 and Cygnus X-1, where high-resolution spectral measurements using Chandra's high-energy transmission grating has made it possible to measure Doppler shifts of 100 km s[superscript -1]. The accuracy of our measurements is consistent with that needed to analyze Chandra observations, exceeding Chandra's 100 km s[superscript -1] limit. Hence, the results presented here not only provide benchmarks for theory, but also accurate rest energies that can be used to determine the bulk motion of material in astrophysical sources. We show the usefulness of our results by applying them to redetermine Doppler shifts from Chandra observations of Vela X-1.United States. National Aeronautics and Space Administration (work orders NNX/2AH84G)United States. Department of Energy (Contract DE-AC52-07NA27344)Smithsonian Astrophysical Observatory (contract SV3-73016
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