Hydrodynamical winds from a spherical two-temperature plasma surrounding a compact object are constructed. The mass-loss rate is computed as a function of electron temperature, optical depth and ...luminosity of the sphere, the values of which can be constrained by the fitting of the spectral energy distributions for known X-ray binary systems. The sensitive dependence of the mass loss rate with these parameters leads to the identification of two distinct regions in the parameter space separating wind-dominated from non wind dominated systems. A critical optical depth, tau_c, as a function of luminosity and electron temperature, is defined which differentiates these two regions. Systems with optical depths significantly smaller than tau_c are wind-dominated. The results are applied to black hole candidate X-ray binary systems in the hard spectral state (Cyg X-1, GX 339-4 and Nova Muscae), and it is found that the inferred optical depth (tau) is similar to tau_c suggesting that they are wind regulated systems. On the other hand, for X-ray binary systems containing a neutron star (e.g., Cyg X-2) tau is much larger than tau_c indicating the absence of significant hydrodynamical winds.
We reexamine evolutionary channels for the formation of binary millisecond pulsars in order to understand their observed orbital period distribution. The available paths provide a natural division ...into systems characterized by long orbital periods (> 60 d) and short orbital periods (< 30 d). Systems with initial periods 1 - 2 d ultimately produce low mass He white dwarfs with short orbital periods (< 1 d). For longer initial periods (> few days), early massive Case B evolution produces CO white dwarfs with orbital periods < 20 d. Common envelope evolution result in short period systems (P < 1 d) from unstable low mass Case B evolution producing He white dwarfs, and from unstable Case C evolution leading to CO white dwarfs. On the other hand, the long orbital period group arises from stable low mass Case B evolution with initial periods > few days producing low mass He white dwarfs and periods > 30 d, and from stable Case C evolution producing CO white dwarfs. The lack of observed systems between 23 and 56 days probably reflects the fact that for comparable initial orbital periods (< few days) low mass Case B and early massive Case B evolution lead to very discrepant final periods. We show in particular that the lower limit (~ 23 d) cannot result from common-envelope evolution.
We consider possible evolutionary models for SS 433. We assume that common-envelope evolution is avoided if radiation pressure is able to expel most of a super-Eddington accretion flow from a region ...smaller than the accretor's Roche lobe. This condition is satisfied, at least initially, for largely radiative donors with masses in the range 4-12 solar masses. For donors more massive than about 5 solar masses, moderate mass ratios q = M_2/M_1 > 1 are indicated, thus tending to favor black-hole accretors. For lower mass donors, evolutionary considerations do not distinguish between a neutron star or black hole accretor. In all cases the mass transfer (and mass loss) rates are much larger than the likely mass-loss rate in the precessing jets. Almost all of the transferred mass is expelled at radii considerably larger than the jet acceleration region, producing the "stationary" H-alpha line, the infrared luminosity, and accounting for the low X-ray luminosity.
