A Turbulent Interstellar Medium Origin of the Binary Period Distribution

Authors:
Robert T. Fisher

Comments: 40 pages, 7 figures

In this paper, we present a semi-empirical model of isolated binary star
formation. This model includes the effects of turbulence in the initial state
of the gas, and has binary orbital parameters consistent with observation. Our
fundamental assumption is that the angular momenta of binary star systems is
directly related to the net angular momentum induced by turbulence in parent
molecular cloud cores. The primary results of this model are as follows. (i) A
quantitative 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 binary
period and mass ratio. (iii) A robust, positive correlation of binary period
and eccentricity. (iv) A robust prediction that the binary separation of
low-mass systems should be more closely separated than those of solar-mass or
larger. These predictions are in good agreement with observations of PMS binary
systems with periods $P > 10^3$ d, which account for the majority of all
binaries.

We conclude with a brief discussion of the implications of our results for
observational and theoretical studies of multiple star formation.

References and citations for this submission:

SLAC-SPIRES HEP (refers to ,
cited by, arXiv reformatted)