A Turbulent Interstellar Medium Origin of the Binary Period Distribution

In this paper, we present a semi-empirical model of isolated binary starformation. This model includes the effects of turbulence in the initial stateof the gas, and has binary orbital parameters consistent with observation. Ourfundamental assumption is that the angular momenta of binary star systems isdirectly related to the net angular momentum induced by turbulence in parentmolecular cloud cores. The primary results of this model are as follows. (i) Aquantitative prediction of the initial width of the binary period distribution($\sigma_{\log {P}_d} = 1.6 - 2.1$ for a star formation efficiency in the range$\epsilon_* = 0.1 - 0.9$). (ii) A robust, negative anticorrelation of binaryperiod and mass ratio. (iii) A robust, positive correlation of binary periodand eccentricity. (iv) A robust prediction that the binary separation oflow-mass systems should be more closely separated than those of solar-mass orlarger. These predictions are in good agreement with observations of PMS binarysystems with periods $P > 10^3$ d, which account for the majority of allbinaries. We conclude with a brief discussion of the implications of our results forobservational and theoretical studies of multiple star formation.Comment: 40 pages, 7 figure