The authors assume a constant Star Formation Rate (0-12Gyr) and a time independent IMF as per \cite{kroupa} . The metallicity parameter [Fe/H] must be held constant for the duration of a BSE code run (i.e. it is age-independent and uniform) so the authors combined several runs with different upper and lower IMF limits in order to mimic the observed [Fe/H] distributions.
\label{par:_f_a_q_e_}
For the BSE software runs, the authors made a simplifying assumption that the function \(f(a,q,e)\) is separable and they assigned various analytic formulae to each of: \(f(a)\) - initial orbit-sizes, \(f(q)\) - initial mass ratios and \(f(e)\) - initial eccentricities.
All parameters for the BSE code were kept at their default values and in order to handle brown dwarfs with a mass below \(0.08 M_{\odot}\) the authors used an extra data grid from Baraffe et al. (1998).
For orbital periods above 5 years, each binary component was evolved separately and a binary was made from two single-star models (S+S) using approximations given by Hurley et al. (2000).
The authors used this parallel S+S approximation as a check on the full BSE models and found the S+S approach gave a roughly similar a-distribution but slightly more short-period pairs then the more detailed BSE calculations.