Binary system

About: Binary system is a research topic. Over the lifetime, 5788 publications have been published within this topic receiving 97882 citations.

The Relative Stability against Merger of Close, Compact Binaries

Abstract: The orbital separation of compact binary stars will shrink with time owing to the emission of gravitational radiation. This inspiral phase of a binary system's evolution generally will be very long compared to the system's orbital period, but the final coalescence may be dynamical and driven to a large degree by hydrodynamic effects, particularly if there is a critical separation at which the system becomes dynamically unstable toward merger. Indeed, if weakly relativistic systems (such as white dwarf-white dwarf binaries) encounter a point of dynamical instability at some critically close separation, coalescence may be entirely a classical, hydrodynamic process. Therefore, a proper investigation of this stage of binary evolution must include three-dimensional hydrodynamic simulations. We have constructed equilibrium sequences of synchronously rotating, equal-mass binaries in circular orbit with a single parameter—the binary separation—varying along each sequence. Sequences have been constructed with various polytropic as well as realistic white dwarf and neutron star equations of state. Using a Newtonian, finite-difference hydrodynamics code, we have examined the dynamical stability of individual models along these equilibrium sequences. Our simulations indicate that no points of instability exist on the sequences we analyzed that had relatively soft equations of state (polytropic sequences with polytropic index n = 1.0 and 1.5 and two white dwarf sequences). However, we did identify dynamically unstable binary models on sequences with stiffer equations of state (n = 0.5 polytropic sequence and two neutron star sequences). We thus infer that binary systems with soft equations of state are not driven to merger by a dynamical instability. For the n = 0.5 polytropic sequence, the separation at which a dynamical instability sets in appears to be associated with the minimum energy and angular momentum configuration along the sequence. Our simulations suggest but do not conclusively demonstrate that, in the absence of relativistic effects, this same association may also hold for binary neutron star systems.

Density and Speed of Sound for Binary Mixtures of a Cyclic Ether with a Butanol Isomer

Abstract: Densities and speeds of sound of the binary mixtures 1,3-dioxolane + 1-butanol, 1,3-dioxolane + 2-butanol, 1,4-dioxane + 1-butanol, and 1,4-dioxane + 2-butanol have been measured at 25 and 40°C. The excess molar volumes and excess isentropic compressibility coefficients were calculated from experimental data and fitted to a Redlich–Kister polynomial function. Results were analyzed in terms of molecular interactions and compared with literature data.

The Mass-Ratio Distribution of Spectroscopic Binary Stars

Abstract: In order to determine the mass-ratio distribution of spectroscopic binary stars, the selection effects that govern the observations of this class of binary systems are investigated. The selection effects are modelled numerically and analytically. The results of the models are compared to the data inThe Eighth Catalogue of the Orbital Elements of Spectroscopic Binary Stars (DAO8) compiled by Battenet al. (1989). The investigations involve binary systems with Main-Sequence primary components only, in order to avoid confusion of evolutionary and selection effects.

Densities and Viscosities of Ethylene Glycol Binary Mixtures at 293.15 K

Abstract: Densities (ρ) and viscosities (η) for the binary mixtures of ethylene glycol with 2-aminoethanol, 2-chloroethanol, 2-ethoxyethanol, benzyl alcohol, pentanol-1, methanol, cyclohexanone, and acetone have been measured over the whole composition range at 293.15 K. The excess volumes and the viscosity deviations were calculated, and the results were fitted to a Redlich−Kister type polynomial relation. The corresponding parameters have been derived. The results were interpreted in terms of specific interactions between the unlike molecules.