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Session 45 - New Insights on X-ray Binaries.
Display session, Wednesday, June 11
South Main Hall,
We present the first global, three dimensional hydrodynamic simulations of Roche lobe overflow (RLOF) and accretion disk dynamics in an HMXB. We use the observed parameters of LMC-X4, a disk-fed X-ray binary undergoing full Roche lobe overflow. We include the Sobolev approximation to the radiatively driven primary wind, as well as first order radiative transfer of a time-dependant, self-consistent X-ray luminosity from the X-ray pulsar. The simulation is initialized with a Roche-filling geometry and a smooth CAK-type wind solution. The simulation is allowed to form its own tidal stream and accretion disk; sufficient time is allowed for the disk to reach a dynamical equilibrium. A disk of compressed primary wind also forms in the orbital plane due to the closeness of the binary orbit and the assumption of co-rotation. The stream is thicker than the accretion disk as it enters, merging with the disk material near the neutron star on the rear (opposite the primary) side. The convergent stream material generates strong spiral shocks within the disk. The simulation sustains Eddington and super-Eddington accretion rates at both a lower and a higher grid resolution in the region of the neutron star. A fast (\approx2000 km/sec), low density wind is driven radiatively from the surface of the accretion disk by the X-rays in the vicinity of the neutron star. This wind completely dominates any thermally driven wind that arrises due to X-ray illumination of the primary surface.
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