  Context: The K2V star eps Eri hosts one known inner planet, an outer Kuiper
belt analog, and an inner disk of warm dust. Spitzer/IRS measurements indicate
that the warm dust is present at distances as close as a few AU from the star.
Its origin is puzzling, since an "asteroid belt" that could produce this dust
would be unstable because of the known inner planet. Aims: Here we test the
hypothesis that the observed warm dust is generated by collisions in the outer
belt and is transported inward by Poynting-Robertson (P-R) drag and strong
stellar winds. Methods: We simulated a steady-state distribution of dust
particles outside 10AU with a collisional code and in the inner region (r<10AU)
with single-particle numerical integrations. By assuming homogeneous spherical
dust grains composed of water ice and silicate, we calculated the thermal
emission of the dust and compared it with observations. We investigated two
different orbital configurations for the inner planet inferred from RV
measurements, one with a highly eccentric orbit of e=0.7 and another one with a
moderate one of e=0.25. We also produced a simulation without a planet.
Results: Our models can reproduce the shape and magnitude of the observed SED
from mid-IR to sub-mm wavelengths, as well as the Spitzer/MIPS radial
brightness profiles. The best-fit dust composition includes both ice and
silicates. The results are similar for the two possible planetary orbits and
without a planet. Conclusions: The observed warm dust in the system can indeed
stem from the outer belt and be transported inward by P-R and stellar wind
drag. The inner planet has little effect on the distribution of dust, so that
the planetary orbit could not be constrained. Reasonable agreement between the
model and observations can only be achieved by relaxing the assumption of
purely silicate dust and assuming a mixture of silicate and ice in comparable
amounts.
