Closed Binary Systems

Binary systems have been the most common system of interest when applying FST. Most investigations of closed binary systems have involved the determination and examination of the three KBIs, possibly followed by some description of local composition or preferential solvation (see Section 1.3.4), all of which is composition dependent. The equations provided in the previous section are more commonly expressed and simpMed by the definition of two additional variables (Ben-Naim 1977), 

If we consider a binary mixture of a solvent (1) and a solute (2), then FST provides the following expressions. 

All the quantities on the left-hand side of the expressions are second derivatives of the Gibbs free energy, while all the quantities on the right-hand side involve second derivatives of pF—the characteristic thermodynamic potential of the grand canonical ensemble. Application of the stability conditions for stable (miscible) solutions indicates that we must have rju 0 and C2 0 (Prigogine and Dufay 1954). 

The above expressions can be manipulated further to provide relationships for the various activity coefficients, 

In many cases, the solute may appear at low concentrations. Limiting values of the above expressions are then 

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Davies, R.E., Pringle, J.E. (1981), Spindown of neutron stars in close binary systems - II , MNRAS 196, 209. 

As it is well known and has been pointed out in a recent review paper (Sahade 1986), all the ultraviolet spectra of close binary systems - except Algols - are characterized by the presence of high temperature resonance doublets of C IV, Si IV and N V, normally in emission, the ions being listed in order of decreasing intensity. 

In the Algols observed outside of eclipse, however, the resonance doublet line appear in absorption and, contrary to what we have described for the rest of the close binary systems, C IV is the weakest of the ions. This fact prompted Peters and Polidan (1984) to advance the idea that in the atmosphere of the more massive components in Algol systems, C is underabundant and N overabundant, in confirmation of Parathasarathy et al s (1983) results. 

It was interesting that a few Algols, namely, U Cep (Plavec 1983), RW Tauri (Plavec and Dobias 1983) and TT Hydrae, U Sge and UX Monocerotis (Plavec et al. 1984) were observed with the IUE satellite at principal eclipse. And on these images the resonance doublets of C IV, Si IV and N V are displayed in emission and, as far as intensities and sequence of intensities go, they behave like in the rest of the close binary systems, that is, C IV is the strongest feature of the three. 

EMPIRICAL DETERMINATION OF THE GRAVITY-DARKENING EXPONENT FOR THE SECONDARY COMPONENTS FILLING THE ROCHE LOBE IN SEMI-DETACHED CLOSE BINARY SYSTEMS... 

Figure 1. Carbon abundance as a function of mass for both components of a close binary system at the onset of mass transfer. The region from Mx=0 to Mr=Mgi=8.1 Mo corresponds to the originally less massive component (gainer), whereas the carbon distribution of the loser is plotted from 8.1 Mo (surface) to 17.1 M (center). The first occurrence of hydrogen depleted layers (Xat<0.7) and the end of the Roche Lobe Overflow are indicated.

Empirical Determination of the Gravity-Darkening Exponent for the Secondary Components Filling the Roche Lobe in Semi-Detached Close Binary Systems... 

We have concentrated in this review on three broad categories of stellar and supernova nucleosynthesis sites (i) the mass range 1 M/M 10 of intermediate -mass stars, for which substantial element production occurs during the AGB phase of their evolution (ii) the mass range M lOM , corresponding to the massive star progenitors of type II ( core collapse ) supernovae and (hi) type la supemovae, which are understood to arise as a consequence of the evolution of intermediate mass stars in close binary systems. 

If one uses the cosmic ray energy requirements and the nonthermal radiation as a guideline, then the most powerful accelerators of relativistic particles in the Galaxy should be supernovae and supernova remnants, pulsars, neutron stars in close binary systems, and winds of young massive stars. The total power Lcr needed to maintain the observed energy density of cosmic rays is estimated as 1041 erg/s. For the acceleration by a supernovae, this estimate... 

For main sequence secondary stars in massive close binary systems, a strong boron depletion must also be expected due to the transfer of nuclear processed matter however, a very noticeable CNO-signature is always present in this case (cf. e.g. de Loore De Greve, 1992). Therefore, the existence of boron depleted stars with a roughly normal nitrogen abundance would be a clear indication of rotational mixing. 

Type la SNe are believed to originate from the C-deflagration of a WD reaching the Chandrasekhar mass (1.44 M0) after accretion of material from a young companion in a close binary system. C-deflagration occurs as a consequence of such accretion and... 

Other perspective spectropolarimetric observations are from a gronp of massive Be and WR stars single as well as components of close binary systems. Data on polarization of their radiation and its changes with time provides valuable information on geometry of extended envelopes of these stars. Spectropolarimetry also enables us to compare the polarization in continuum and in bright lines that help to distingrrish between different components intrirrsic and interstellar in observe d polarization and to understand the mechanism of their generation. 

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