  Lomax et al. have constructed an ensemble of 60 prestellar cores having
masses, sizes, projected shapes, temperatures and non-thermal radial velocity
dispersions that match, statistically, the cores in Ophiuchus; and have
simulated the evolution of these cores using SPH. Each core has been evolved
once with no radiative feedback from stars, once with continuous radiative
feedback, and once with episodic radiative feedback. Here we analyse the
multiplicity statistics from these simulations. With episodic radiative
feedback, (i) the multiplicity frequency is ~60% higher than in the field; (ii)
the multiplicity frequency and the mean semi-major axis both increase with
primary mass; (iii) one third of multiple systems are hierarchical systems with
more than two components; (iv) in these hierarchical systems the inner pairings
typically have separations of a few au and mass ratios concentrated towards
unity, whereas the outer pairings have separations of order 100 au and a
flatter distribution of mass ratios. The binary statistics are compatible with
observations of young embedded populations, and -- if wider orbits are
disrupted preferentially by external perturbations -- with observations of
mature field populations. With no radiative feedback, the results are similar
to those from simulations with episodic feedback. With continuous radiative
feedback, brown dwarfs are under-produced, the number of multiple systems is
too low, and the statistical properties of multiple systems are at variance
with observation. This suggests that star formation in Ophiuchus may only be
representative of global star formation if accretion onto protostars, and hence
radiative feedback, is episodic.

Solar and Stellar Astrophysics