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K. J. Walsh, D. C. Richardson (U. of Maryland)
We present numerical simulations of near-Earth asteroid (NEA) tidal disruption resulting in bound, mutually orbiting systems. Using a rubble pile model we have constrained the relative likelihoods for possible physical and dynamical properties of the binaries created. Overall 110,500 simulations were run, with each body consisting of 1000 particles. The encounter parameters of close approach distance and velocity were varied, as were the bodies' spin, elongation and spin axis direction. The binary production rate increases for closer encounters, at lower speeds, for more elongated bodies, and for bodies with greater spin.
The semi-major axes for resultant binaries are peaked between 5--20 primary radii, and there is an overall trend for high eccentricity. The secondary-to-primary size ratios of the simulated binaries are peaked between 0.1 and 0.2, similar to trends among observed asteroid binaries. The spin rates of the primary bodies are narrowly distributed between 3.5 and 6 hour periods, whereas the secondaries' periods are more evenly distributed and can exceed 15 hour periods. These physical properties are compared with various evolutionary forces and dynamical lifetimes to create a model of the expected binary population.
This work presents results that suggest tidal disruption of gravitational aggregates can make binaries physically similar to those currently observed in the NEA population. As well, tidal disruption may create an equal number of binaries with qualities different from those observed, mostly binaries with large separation and with elongated primaries. This material is based upon work supported by the National Science Foundation under Grant No. AST0307549.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.