  Carbon-enhanced metal-poor (CEMP) stars count for 9-25% of all the very
metal-poor stars of the halo. In at least some CEMP stars the chemical
enrichment is believed to be due to wind mass transfer in the past from an AGB
donor star on to a low-mass companion. However, binary population synthesis
models predict much lower CEMP fractions. As an alternative to the canonical
Bondi-Hoyle-Lyttleton (BHL) wind accretion model, recent hydrodynamical
simulations suggest an efficient mode of wind mass transfer, called wind
Roche-lobe overflow (WRLOF), can reproduce observations of AGB winds in binary
systems. We use our population synthesis model to test the consequences of
WRLOF on a population of CEMP stars. Compared to previous predictions based on
the BHL model we find a modest increase of the fraction of CEMP stars and
substantial differences in the distributions of carbon and periods in the
population of CEMP stars.
