  Scattered light images of the optically thin dust disk around the 5 Myr old
star HD141569 have revealed its complex asymmetric structure. We show in this
paper that the surface density inferred from the observations presents
similarities with that expected from a circumprimary disk within a highly
eccentric binary system. We assume that either the two M stars in the close
vicinity of HD141569 are bound companions or at least one of them is an
isolated binary companion. We discuss the resulting interaction with an
initially axisymmetric disk. This scenario accounts for the formation of a
spiral structure, a wide gap in the disk and a broad faint extension outside
the truncation radius of the disk after 10-15 orbital periods with no need for
massive companion(s) in the midst of the disk resolved in scattered light. The
simulations match the observations and the star age if the perturber is on an
elliptic orbit with a periastron distance of 930 AU and an eccentricity from
0.7 to 0.9. We find that the numerical results can be reasonably well
reproduced using an analytical approach proposed to explain the formation of a
spiral structure by secular perturbation of a circumprimary disk by an external
bound companion. We also interpret the redness of the disk in the visible
reported by Clampin et al.(2003) and show that short-lived grains one order of
magnitude smaller than the blow-out size limit are abundant in the disk. The
most probable reason for this is that the disk sustains high collisional
activity. Finally we conclude that additional processes are required to clear
out the disk inside 150 AU and that interactions with planetary companions
possibly coupled with the remnant gas disk are likely candidates.

Astrophysics