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At least 1,099 records · Page 61
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DOE OSTI2015

A systematic study of segregation for Zn{sub x}Bi{sub 1−x} liquid binary alloys

We have investigated the segregating properties of Zn{sub x}Bi{sub 1−x} liquid binary alloys through the thermodynamic route that involves both energy of mixing and entropy of mixing. The perturbation approach is used for effective numerical calculations. Results of our calculations agree well with corresponding experimental data for energy and entropy of mixing in the mixed state. The final prediction of segregating properties such as critical concentration and critical temperature also matches reasonably well with experimental data. Most importantly, both energy of mixing and entropy of mixing have produced almost same values for critical concentration and critical temperature of segregation and thus confirm the reliability of the present approach.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

An experimental study of energy dependence of saturation thickness of multiply scattered gamma rays in binary alloys

The present measurements are carried out to investigate the multiple scattering of 662 keV gamma photons emerging from targets of binary alloys (brass and soldering material). The scattered photons are detected by 51 mm × 51 mm NaI(Tl) scintillation detector whose response unscrambling converting the observed pulse–height distribution to a true photon energy spectrum, is obtained with the help of 10 × 10 inverse response matrix. The numbers of multiply scattered events, having same energy as in the singly scattered distribution, first increases with target thickness and then saturate. The application of response function of scintillation detector does not result in any change of measured saturation thickness. Monte Carlo calculation supports the present experimental results.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Revisiting galactic black hole binary GX 339-4 by using 2007 – 2014 Swift XRT observations

This work aims to study the X-ray properties of the galactic black hole binary GX 339-4. Focus of the study is on exploration of data from Swift-XRT in exclusively photon-counting mode. We use data from 2007 up to August 2014, which contain about 40 pointing observations with level 1 data. The flux of GX 339-4 varies in a factor of 100 during this period of observations. For the purpose of this work, we also try to develop a system to conduct standard SWIFT XRT data reduction automatically, in order to greatly reduce time when working with data bulk, which produces images, lightcurves as well as spectra. We also develop another system to conduct fitting of bulk spectral data with a two-component model, disk blackbody and power-law. The fitting results show that no data have a reduced chi-squared > 2. The fraction of the disk to total flux and the power-law to total flux range from 0.00389 – 0.994 and 0.00605 – 0.996, respectively. From the analysis of the disk component, we obtain the value of the innermost disk radius that does not show any large scale truncation which is in a good agreement with a previous study that used 2007 – 2011 Swift-XRT data, indicating that the systems we developed work properly.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Explicit expressions of self-diffusion coefficient, shear viscosity, and the Stokes-Einstein relation for binary mixtures of Lennard-Jones liquids

Explicit expressions of the self-diffusion coefficient, D{sub i}, and shear viscosity, η{sub sv}, are presented for Lennard-Jones (LJ) binary mixtures in the liquid states along the saturated vapor line. The variables necessary for the expressions were derived from dimensional analysis of the properties: atomic mass, number density, packing fraction, temperature, and the size and energy parameters used in the LJ potential. The unknown dependence of the properties on each variable was determined by molecular dynamics (MD) calculations for an equimolar mixture of Ar and Kr at the temperature of 140 K and density of 1676 kg m{sup −3}. The scaling equations obtained by multiplying all the single-variable dependences can well express D{sub i} and η{sub sv} evaluated by the MD simulation for a whole range of compositions and temperatures without any significant coupling between the variables. The equation for D{sub i} can also explain the dual atomic-mass dependence, i.e., the average-mass and the individual-mass dependence; the latter accounts for the “isotope effect” on D{sub i}. The Stokes-Einstein (SE) relation obtained from these equations is fully consistent with the SE relation for pure LJ liquids and that for infinitely dilute solutions. The main differences from the original SE relation are the presence of dependence on the individual mass and on the individual energy parameter. In addition, the packing-fraction dependence turned out to bridge another gap between the present and original SE relations as well as unifying the SE relation between pure liquids and infinitely dilute solutions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Mutual diffusion of binary liquid mixtures containing methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride

Mutual diffusion coefficients of all 20 binary liquid mixtures that can be formed out of methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride without a miscibility gap are studied at ambient conditions of temperature and pressure in the entire composition range. The considered mixtures show a varying mixing behavior from almost ideal to strongly non-ideal. Predictive molecular dynamics simulations employing the Green-Kubo formalism are carried out. Radial distribution functions are analyzed to gain an understanding of the liquid structure influencing the diffusion processes. It is shown that cluster formation in mixtures containing one alcoholic component has a significant impact on the diffusion process. The estimation of the thermodynamic factor from experimental vapor-liquid equilibrium data is investigated, considering three excess Gibbs energy models, i.e., Wilson, NRTL, and UNIQUAC. It is found that the Wilson model yields the thermodynamic factor that best suits the simulation results for the prediction of the Fick diffusion coefficient. Four semi-empirical methods for the prediction of the self-diffusion coefficients and nine predictive equations for the Fick diffusion coefficient are assessed and it is found that methods based on local composition models are more reliable. Finally, the shear viscosity and thermal conductivity are predicted and in most cases favorably compared with experimental literature values.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Structure and component dynamics in binary mixtures of poly(2-(dimethylamino)ethyl methacrylate) with water and tetrahydrofuran: A diffraction, calorimetric, and dielectric spectroscopy study

We have combined X-ray diffraction, neutron diffraction with polarization analysis, small angle neutron scattering, differential scanning calorimetry, and broad band dielectric spectroscopy to investigate the structure and dynamics of binary mixtures of poly (2-(dimethylamino)ethyl methacrylate) with either water or tetrahydrofuran (THF) at different concentrations. Aqueous mixtures are characterized by a highly heterogeneous structure where water clusters coexist with an underlying nano-segregation of main chains and side groups of the polymeric matrix. THF molecules are homogeneously distributed among the polymeric nano-domains for concentrations of one THF molecule/monomer or lower. A more heterogeneous situation is found for higher THF amounts, but without evidences for solvent clusters. In THF-mixtures, we observe a remarkable reduction of the glass-transition temperature which is enhanced with increasing amount of solvent but seems to reach saturation at high THF concentrations. Adding THF markedly reduces the activation energy of the polymer β-relaxation. The presence of THF molecules seemingly hinders a slow component of this process which is active in the dry state. The aqueous mixtures present a strikingly broad glass-transition feature, revealing a highly heterogeneous behavior in agreement with the structural study. Regarding the solvent dynamics, deep in the glassy state all data can be described by an Arrhenius temperature dependence with a rather similar activation energy. However, the values of the characteristic times are about three orders of magnitude smaller for THF than for water. Water dynamics display a crossover toward increasingly higher apparent activation energies in the region of the onset of the glass transition, supporting its interpretation as a consequence of the freezing of the structural relaxation of the surrounding matrix. The absence of such a crossover (at least in the wide dynamic window here accessed) in THF is attributed to the lack of cooperativity effects in the relaxation of these molecules within the polymeric matrix.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Effect of intrinsic curvature and edge tension on the stability of binary mixed-membrane three-junctions

We use a combination of coarse-grained molecular dynamics simulations and theoretical modeling to examine three-junctions in mixed lipid bilayer membranes. These junctions are localized defect lines in which three bilayers merge in such a way that each bilayer shares one monolayer with one of the other two bilayers. The resulting local morphology is non-lamellar, resembling the threefold symmetric defect lines in inverse hexagonal phases, but it regularly occurs during membrane fission and fusion events. We realize a system of junctions by setting up a honeycomb lattice, which in its primitive cell contains two hexagons and four three-line junctions, permitting us to study their stability as well as their line tension. We specifically consider the effects of lipid composition and intrinsic curvature in binary mixtures, which contain a fraction of negatively curved lipids in a curvature-neutral background phase. Three-junction stability results from a competition between the junction and an open edge, which arises if one of the three bilayers detaches from the other two. We show that the stable phase is the one with the lower defect line tension. The strong and opposite monolayer curvatures present in junctions and edges enhance the mole fraction of negatively curved lipids in junctions and deplete it in edges. This lipid sorting affects the two line tensions and in turn the relative stability of the two phases. It also leads to a subtle entropic barrier for the transition between junction and edge that is absent in uniform membranes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR BF DRACONIS

BF Dra is now known to be an eccentric double-lined F6+F6 binary star with relatively deep (0.7 mag) partial eclipses. Previous studies of the system are improved with 7494 differential photometric observations from the URSA WebScope and 9700 from the NFO WebScope, 106 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope and the 1 m coude-feed spectrometer at Kitt Peak National Observatory, and 31 accurate radial velocities from the CfA. Very accurate (better than 0.6%) masses and radii are determined from analysis of the two new light curves and four radial velocity curves. Theoretical models match the absolute properties of the stars at an age of about 2.72 Gyr and [Fe/H] = -0.17, and tidal theory correctly confirms that the orbit should still be eccentric. Our observations of BF Dra constrain the convective core overshooting parameter to be larger than about 0.13 H{sub p}. We find, however, that standard tidal theory is unable to match the observed slow rotation rates of the components' surface layers.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

OPTICAL AND NEAR-INFRARED MONITORING OF THE BLACK HOLE X-RAY BINARY GX 339-4 DURING 2002-2010

We present the optical/infrared (O/IR) light curve of the black hole X-ray binary GX 339-4 collected at the SMARTS 1.3 m telescope from 2002 to 2010. During this time the source has undergone numerous state transitions including hard-to-soft state transitions when we see large changes in the near-IR flux accompanied by modest changes in optical flux, and three rebrightening events in 2003, 2005, and 2007 after GX 339-4 transitioned from the soft state to the hard. All but one outburst show similar behavior in the X-ray hardness-intensity diagram. We show that the O/IR colors follow two distinct tracks that reflect either the hard or soft X-ray state of the source. Thus, either of these two X-ray states can be inferred from O/IR observations alone. From these correlations we have constructed spectral energy distributions of the soft and hard states. During the hard state, the near-IR data have the same spectral slope as simultaneous radio data when GX 339-4 was in a bright optical state, implying that the near-IR is dominated by a non-thermal source, most likely originating from jets. Non-thermal emission dominates the near-IR bands during the hard state at all but the faintest optical states, and the fraction of non-thermal emission increases with increasing optical brightness. The spectral slope of the optical bands indicate that a heated thermal source is present during both the soft and hard X-ray states, even when GX 339-4 is at its faintest optical state. We have conducted a timing analysis of the light curve for the hard and soft states and find no evidence of a characteristic timescale within the range of 4-230 days.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

CHEMICAL COMPOSITION OF THE COMPONENTS OF ECLIPSING BINARY STAR ZZ BOOTIS

We investigated ZZ Boo using a high-resolution (R = 80,000) spectrum obtained at the BOES echelle spectrograph attached to a 1.8 m telescope at the Bohuynsan observatory in Korea. The atmospheric parameters of the components were found using the published photometrical observations and the abundance analysis of iron lines: the flux ratio of the components F{sub A} /F{sub B} = 1.12 {+-} 0.15, the effective temperatures of the components T{sub eff} = 6860 {+-} 20 K and 6930 {+-} 20 K, the surface gravities log g = 3.72 {+-} 0.10 and 3.84 {+-} 0.10, the metallicities [Fe/H] = -0.10 {+-} 0.08 and -0.03 {+-} 0.10, and the projected rotation velocities vsin i = 11.9 {+-} 0.4 km s{sup -1} and 19.3 {+-} 0.8 km s{sup -1} for the primary and secondary components, respectively. The pointed errors are the formal errors of the methods used; the systematic errors of the temperatures, gravities, metallicities, and projected rotational velocities can be as high as 250-300 K, 0.3 dex, 0.15 dex, and 4 km s{sup -1}, respectively. The abundances of 24 and 22 chemical elements were determined in the atmospheres of the components. The abundance pattern of the primary component shows the solar or slightly undersolar abundances of all elements. CNO abundances are close to solar values. The abundance pattern of this component resembles those of {lambda} Boo type stars. The abundances of light elements, except oxygen, in the atmosphere of the secondary component are practically solar. The abundances of barium and two detected lanthanides are close to the solar values; the overabundance of oxygen is 0.9 dex. The abundances of two components are evidently different. The comparison of relative abundances with the condensation temperatures and second ionization potentials of the elements confirms the difference in abundance patterns and allows discussion of the different accretion scenarios for two components of this binary system.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

PHOTOMETRIC PROPERTIES FOR SELECTED ALGOL-TYPE BINARIES. IV. AV HYDRAE AND DZ CASSIOPEIAE

We present BVR photometric observations and several eclipsing times for AV Hya and DZ Cas from 2004 to 2011. Using the Wilson-Devinney method, the photometric solutions with hot spots were deduced from their asymmetric light curves. The results indicate that both stars are Algol-type binaries, whose mass ratio, q{sub ph}, and fill-out factor of the primary, f{sub 1}, are q{sub ph} = 0.255({+-} 0.002) and f{sub 1} = 81.2({+-} 0.2)% for AV Hya, and q{sub ph} = 0.093({+-} 0.003) and f{sub 1} = 98.7({+-} 0.3)% for DZ Cas. Based on all available light minimum times, it is discovered that the O - C curve of each star could be described by a light-time orbit overlying on a downward parabola. Their periods and amplitudes are P{sub 3} = 37.2({+-} 0.7) yr and A = 0fd0095({+-}0fd0006) for AV Hya, and P{sub 3} = 62.5({+-} 1.0) yr and A = 0fd0183({+-}0fd0007) for DZ Cas. Cyclic variations may result from the light-time effect due to the third body. The secular period decrease rates are dP/dt = -1.47({+-} 0.04) Multiplication-Sign 10{sup -7} days yr{sup -1} for AV Hya and dP/dt = -0.92({+-} 0.04) Multiplication-Sign 10{sup -7} days yr{sup -1} for DZ Cas. This may be interpreted using mass and angular momentum loss from the system. With decreasing period, the fill-out factor of the primary increases and it may finally fill its inner Roche lobe. Therefore, AV Hya and DZ Cas with a secular period decrease will evolve from semi-detached configurations into contact ones.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

ABSOLUTE PROPERTIES OF THE ECLIPSING BINARY STAR V335 SERPENTIS

V335 Ser is now known to be an eccentric double-lined A1+A3 binary star with fairly deep (0.5 mag) partial eclipses. Previous studies of the system are improved with 7456 differential photometric observations from the URSA WebScope and 5666 from the NFO WebScope, and 67 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope. From dates of minima, the apsidal period is about 880 years. Accurate (better than 2%) masses and radii are determined from analysis of the two new light curves and the radial velocity curve. Theoretical models match the absolute properties of the stars at an age of about 380 Myr, though the age agreement for the two components is poor. Tidal theory correctly confirms that the orbit should still be eccentric, but we find that standard tidal theory is unable to match the observed asynchronous rotation rates of the components' surface layers.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

DISCOVERY OF TWO VERY WIDE BINARIES WITH ULTRACOOL COMPANIONS AND A NEW BROWN DWARF AT THE L/T TRANSITION

We present the discovery and spectroscopic follow-up of a nearby late-type L dwarf (2M0614+3950), and two extremely wide very low mass binary systems (2M0525-7425AB and 2M1348-1344AB), resulting from our search for common proper motion pairs containing ultracool components in the Two Micron All Sky Survey and the Wide-field Infrared Survey Explorer catalogs. The near-infrared spectrum of 2M0614+3950 indicates a spectral type L9 {+-} 1 object residing at a distance of 26.0 {+-} 1.8 pc. The optical spectrum of 2M0525-7425A reveals an M3.0 {+-} 0.5 dwarf primary, accompanied by a secondary previously classified as L2. The system has an angular separation of {approx}44'', equivalent to {approx}2000 AU at a distance of 46.0 {+-} 3.0 pc. Using optical and infrared spectra, respectively, we classify the components of 2M1348-1344AB as M4.5 {+-} 0.5 and T5.5 {+-} 1. The angular separation of {approx}68'' is equivalent to {approx}1400 AU at a distance of 20.7 {+-} 1.4 pc. 2M1348-1344AB is one of only six very wide (separation >1000 AU) systems containing late T dwarfs known to date.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

BVR{sub c}I{sub c} OBSERVATIONS AND ANALYSES OF THE DWARF DETACHED BINARY V1043 CASSIOPEIA AND A COMMENT ON PRECONTACT W UMa'S

Complete Bessel BVR{sub c}I{sub c} light curves of V1043 Cassiopeia [2MASS J00371195+5301324, Mis V1292, USNO-A2.0 1425-00875743, {alpha}(2000) = 00{sup h}37{sup m}11.{sup s}95, {delta}(2000) = +53 Degree-Sign 01'32.''5] are analyzed. The system is a member of the small group of pre-contact W UMa binaries (PCWBs). Its light curve has the appearance of an Algol (EA) light curve, however it is made up of dwarf solar type components in a detached mode with a period of only 0.6616 days. The analysis includes a period study, an improved ephemeris, a mass ratio search, and a simultaneous BVR{sub c}I{sub c} Wilson-Devinney solution. We document about 20 other PCWBs given in the literature. Several have RS CVn-like properties.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

THE CLUSTER AGES EXPERIMENT (CASE). V. ANALYSIS OF THREE ECLIPSING BINARIES IN THE GLOBULAR CLUSTER M4

We use photometric and spectroscopic observations of the eclipsing binaries V65, V66, and V69 in the field of the globular cluster M4 to derive masses, radii, and luminosities of their components. The orbital periods of these systems are 2.29, 8.11, and 48.19 days, respectively. The measured masses of the primary and secondary components (M{sub p} and M{sub s} ) are 0.8035 {+-} 0.0086 and 0.6050 {+-} 0.0044 M{sub Sun} for V65, 0.7842 {+-} 0.0045 and 0.7443 {+-} 0.0042 M{sub Sun} for V66, and 0.7665 {+-} 0.0053 and 0.7278 {+-} 0/0048 M{sub Sun} for V69. The measured radii (R{sub p} and R{sub s} ) are 1.147 {+-} 0.010 and 0.6110 {+-} 0.0092 R{sub Sun} for V66, 0.9347 {+-} 0.0048 and 0.8298 {+-} 0.0053 R{sub Sun} for V66, and 0.8655 {+-} 0.0097 and 0.8074 {+-} 0.0080 R{sub Sun} for V69. The orbits of V65 and V66 are circular, whereas that of V69 has an eccentricity of 0.38. Based on systemic velocities and relative proper motions, we show that all three systems are members of the cluster. We find that the distance to M4 is 1.82 {+-} 0.04 kpc-in good agreement with recent estimates based on entirely different methods. We compare the absolute parameters of V66 and V69 with two sets of theoretical isochrones in mass-radius and mass-luminosity diagrams, and for assumed [Fe/H] = -1.20, [{alpha}/Fe] = 0.4, and Y = 0.25 we find the most probable age of M4 to be between 11.2 and 11.3 Gyr. Color-magnitude diagram (CMD) fitting with the same parameters yields an age close to, or slightly in excess of, 12 Gyr. However, considering the sources of uncertainty involved in CMD fitting, these two methods of age determination are not discrepant. Age and distance determinations can be further improved when infrared eclipse photometry is obtained.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

THE SPECTROSCOPIC ORBITS OF FIVE SOLAR-TYPE, SINGLE-LINED BINARIES

We have determined spectroscopic orbits for five single-lined spectroscopic binaries, HD 100167, HD 135991, HD 140667, HD 158222, HD 217924. Their periods range from 60.6 to 2403 days and the eccentricities from 0.20 to 0.84. Our spectral classes for the stars confirm that they are of solar type, F9-G5, and all are dwarfs. Their [Fe/H] abundances, determined spectroscopically, are close to the solar value and on average are 0.12 greater than abundances from a photometric calibration. Four of the five stars are rotating faster than their predicted pseudosynchronous rotational velocities.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

BINARITY AND PULSATION IN ALGOL-TYPE BINARY SYSTEM SX DRACONIS

Photometric observations of SX Dra were carried out to determine the properties of the components and pulsational characteristics of the more massive pulsational component. Physical parameters of the component stars were obtained by modeling B and V light curves using the Wilson-Devinney code. Results indicate that SX Dra is a semi-detached system with the secondary component filling its Roche lobe. The O-C data showed parabolic and sinusoidal variation. Cyclic variation in the O-C diagram could be the result of the possible magnetic activity of the secondary component instead of the third body. The secular increase in the orbital period of the system can be interpreted as being the result of mass transfer from the secondary component to the primary one at a rate of 2.1 Multiplication-Sign 10{sup -7} M{sub Sun} yr{sup -1}. Results of a time-series analysis performed after removing binary effects indicated that the hot component shows {delta} Scuti light variations with pulsational periods of 63 and 73 minutes. Spherical harmonic degrees (l) were determined to be 3 for the first frequency and 1-2 for the second frequency.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

PHOTOMETRIC PROPERTIES OF THE INTERACTING BINARY BO MONOCEROTIS: EVIDENCE FOR MAGNETIC ACTIVITY

BO Monocerotis (BO Mon) is a severely neglected short-period (2.23 days) Algol-type eclipsing binary star system undergoing angular momentum variations that are likely due to the evolved secondary star experiencing cycles of magnetic activity. We present the first CCD light curves of BO Mon, which were observed at the Kutztown University Observatory (Kutztown, PA) in 2012 using B, V, and I filters. The analysis presented here is the first of its kind for BO Mon and provides the first physical model of the system's parameters. We also incorporate over 40 yr of published times of minimum light to provide a new ephemeris curve and perform a period study that greatly improves, while differing significantly from, an earlier ephemeris analysis that was done more than 13 yr ago. The observed variations in BO Mon's orbital period supply evidence for mass transfer and magnetic activity and our photometric model affords the basic properties of the system for use in future photometric and spectroscopic studies.

79 ASTRONOMY AND ASTROPHYSICS↗