Adaptative optics imaging of the Frosty Leo nebula.

Images of IRAS 09371+1212 (the Frosty Leo nebula) have been obtained in the near infrared (K' band) with the COME-ON+ adaptative optics system. These high resolution pictures confirm the formerly established characteristics and unveil unknown details of the nebula. For the first time the central star is directly resolved against the disk-like structure of the equatorial plane. Though large scale isophotes are symmetric, short scale isophotes are asymmetric with respect to the star. This may be the signature of perturbations by a companion to the central object. Although no direct imaging of the binary system has been possible, this interpretation leads to the derivation of dynamics parameters that appears consistent with an unseen companion of 1.4M_sun_<M_comp_<2.6M_sun. It is established that the source of the mass loss is the directly imaged star. The nebula is thus composed of a binary system embedded in a circumbinary disk. The presence of the disk is not clearly explained yet. A complete explanation of the system history is not yet available but we suggest some possible scenarii.