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Session 43 - Binary Stars.
Display session, Tuesday, January 16
North Banquet Hall, Convention Center
High-mass X-ray binary (HMXB) systems are often subdivided into two classes: wind accreting systems, where the primary surface lies well within its Roche lobe, and Roche lobe overflow (RLOF) systems, where the primary has exceeded the critical surface. These are really only the two extremes of one continuum process; as the primary swells and its Roche lobe tightens due to mass loss, the system will move along this continuum. We present a series of two-dimensional hydrodynamic simulations of HMXBs for different values of the Roche overflow parameter \lambda = \phi_surface/\phi_critical, the ratio of gravitational potential at the primary surface to that of the critical surface. New to these simulations is the inclusion of radiative transfer and radiation pressure of the X-rays, as well as a time-variable X-ray luminosity that is determined by the mass accretion rate. When the primary lies well within its critical surface we find negligible tidal mass loss enhancement, and a system that is characterized by wind accretion with the development of a photoionization zone around the compact object, as well as a strong accretion wake behind the object. For moderate values of \phi_surface/\phi_critical we observe tidally enhanced mass loss via a thin tidal stream, resulting in higher accretion wake densities for thinner streams, and the driving of a stream-fed X-ray heated thermal wind from the collapsed companion for thicker streams. For \lambda near 1.0 we observe the development of a steady accretion disk characterized by a total shadowing of the X-rays in the orbital plane.
