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Session 60 - Multiple Stars.
Display session, Wednesday, June 12
High mass X-ray binary star systems with elliptical orbits, like GX301-2, often exhibit a peak in X-ray luminosity during periastron passage. In the past, two models have been presented to explain this phenomenon. The first is a gradual increase in density of the accreting stellar wind as the neutron star approaches periastron, the second is "Roche" lobe overflow occuring near periastron We present two dimensional simulations of the highly eccentric X-ray transient system GX301-2. The model required extensive modification from previous models of X-ray binaries in circular orbits, to account for changes in orbital speed, binary separation, and tidal distortion. Our model predicts enhanced mass loss from the primary star due to "Roche" lobe overflow. Much of the tidally stripped gas falls back onto the primary star, and some is ejected from the binary system. The remaining mass forms a thick accretion disk shortly after periastron, and for the remainder of the orbit the mass in the accretion disk decreases from a combination of ablation by the stellar wind and mass accretion. For the parameters used in this model, the resulting evolution in the accretion driven X-ray luminosity shows a strong increase occuring near periastron and lasting for roughly half an orbit. The model also predicts a sharp increase in absorbtion near periastron that gradually decreases during the rest of the orbit.
Program listing for Wednesday