Evaluating the impact of binary parameter uncertainty on stellar
  population properties
  Binary stars have been shown to have a substantial impact on the integrated
light of stellar populations, particularly at low metallicity and early ages -
conditions prevalent in the distant Universe. But the fraction of stars in
stellar multiples as a function of mass, their likely initial periods and
distribution of mass ratios are all known empirically from observations only in
the local Universe. Each has associated uncertainties. We explore the impact of
these uncertainties in binary parameters on the properties of integrated
stellar populations, considering which properties and timescales are most
susceptible to uncertainty introduced by binary fractions and whether
observations of the integrated light might be sufficient to determine binary
parameters. We conclude that the effects of uncertainty in the empirical binary
parameter distributions are likely smaller than those introduced by metallicity
and stellar population age uncertainties for observational data. We identify
emission in the He II 1640 Angstrom emission line and continuum colour in the
ultraviolet-optical as potential indicators of a high mass binary presence,
although poorly constrained metallicity, dust extinction and degeneracies in
plausible star formation history are likely to swamp any measurable signal.
