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Session 105 - Pre-Main Sequence Binaries and Disks.
Display session, Thursday, January 18
North Banquet Hall, Convention Center

[105.03] Energetics of Star--Disc Encounters in the Non-linear Regime

S. M. Hall, C. J. Clarke, J. E. Pringle (IoA)

We investigate the response of a circumstellar accretion disc to the fly-by of a perturbing mass on a parabolic orbit. The energy and angular momentum transferred during the encounter are calculated using a reduced three-body method. In almost all close encounters the energy and angular momentum transfer is dominated by disc material becoming unbound from the system, with the contributions from close disc particle -- star encounters being significant. For more distant encounters with some prograde element to the motion the disc material loses energy and angular momentum to the perturber's orbit through a resonance feature. The magnitude of the energy transfer calculated in our simulations is greater than that of the binding energy of material exterior to periastron by a factor of two in the prograde case, and up to a factor of five in the case of the retrograde encounter. The destructive nature of the encounters indicates that a non-linear treatment is essential in all but the most distant encounters. We have also performed some calculations taking into account the effect of including the reaction of the binary orbit to the disc material during the encounter as well as investigating the potential importance of hydrodynamic effects.

Program listing for Thursday