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Session 110 - X-ray, Binaries & Accretion Disks.
Display session, Saturday, January 10
Exhibit Hall,

[110.18] The Accretion Disk Limit Cycle Mechanism in the Black Hole X-ray Binaries

J. K. Cannizzo (NASA/GSFC/USRA)

We present computations using a time dependent model for the accretion disk limit cycle mechanism in the black hole X-ray binaries, paying attention to systematic effects so as to probe the limitations or extent to which models of this type can be trusted. This model is the most promising explanation for the large outbursts lasting several hundred days seen in these systems. In particular we look at the issues of (i) the grid spacing required in the models, (ii) the deviation from steady state flow within the disk, (iii) the outburst rise time versus triggering location, (iv) the long term light curves, including evaporation from the inner disk, and (v) the strength of irradiation. We synthesize the lessons learned from these areas to form preliminary overview of the global picture. Our primary conclusions are that (i) more than about 500 radial grid points are required, (ii) the analytical model of Vishniac amp; Wheeler to model the cooling fronts seems valid, (iii) the outbursts must trigger at a radius exceeding about 10^10 cm, (iv) evaporation served to lengthen the recurrence times, and (v) irradiation is not a strong effect as regards the disk kinematics.

The work was supported through the long-term scientist program under the Universities Space Research Association (USRA contract NAS5-32484) in the Laboratory for High Energy Astrophysics at Goddard Space Flight Center, and will appear in the Feb 10, 1998 issue of the Astrophysical Journal.

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Program listing for Saturday