A CRASH simulation of the contribution of binary stars to the epoch of
  reionization
  We use a set of 3D radiative transfer simulations to study the effect that a
large fraction of binary stars in galaxies during the epoch of reionization has
on the physical properties of the intergalactic medium (i.e. the gas
temperature and the ionization state of hydrogen and helium), on the topology
of the ionized bubbles and on the 21 cm power spectra. Consistently to previous
literature, we find that the inclusion of binary stars can speed up the
reionization process of HI and HeI, while HeII reionization is still dominated
by more energetic sources, especially accreting black holes. The earlier
ionization attained with binary stars allows for more time for cooling and
recombination, so that gas fully ionized by binary stars is typically colder
than that ionized by single stars at any given redshift. With the same volume
averaged ionization fraction, the inclusion of binary stars results in fewer
small ionized bubbles and more large ones, with visible effects also on the
large scales of the 21 cm power spectrum.
