35th Meeting of the AAS Division on Dynamical Astronomy, April 2004
Session 1 Extra-solar Planets
Oral, Tuesday, April 20, 2004, 9:30am-12:45pm,

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[1.02] The Decay of Accreting Triple Systems as Brown Dwarf Formation Scenario

S. Umbreit (Max-Planck-Institut für Astronomie Heidelberg), R. Spurzem (Astronomisches Rechen-Institiut Heidelberg), A. Burkert (Universitäts-Sternwarte München), T. Henning (Max-Planck-Institut für Astronomie Heidelberg)

We investigate the dynamical decay of non-hierarchical accreting triple systems and its implications on the ejection model as Brown Dwarf formation scenario. A modified chain-regularisation scheme is used to integrate the equations of motion, that also allows for mass changes over time as well as for momentum transfer from the accreted gas mass onto the bodies. We integrate an ensemble of triple systems within a certain volume with different accretion rates, assuming several prescriptions of how momentum is transfered onto the bodies. We follow their evolution until the systems have decayed and are outside an assumed cloud region. We analyse the end states and decay times of these systems and determine the fraction of Brown Dwarfs formed, their escape speeds as well as the semi-major axis distribution of the formed Brown Dwarf binaries. We find, depending on the assumed momentum transfer model, a formation probability of Brown Dwarfs of up to 86% in our simulations which is almost 3 times higher than predicted by a previous analytical estimate in the literature. Furthermore, our obtained semi-major axis distribution is in remarkable agreement to observations. The difference seen in our results from previous analytical estimates is related to the shrinking of and momentum transfer in the systems. We conclude that accretion and momentum transfer of accreted gas during the dynamical decay of triple systems is able to produce a high fraction of substellar objects, making the ejection model a viable option as Brown Dwarf formation scenario.

The author(s) of this abstract have provided an email address for comments about the abstract: umbreit@mpia.de

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Bulletin of the American Astronomical Society, 36 #2
© 2004. The American Astronomical Soceity.