The Shaping of the Red Rectangle Proto-Planetary Nebula
  I argue that the slowly expanding biconical structure of the Red Rectangle--a nebula around the post asymptotic giant branch binary stellar system HD 44179--can be formed by intermittent jets blown by the accreting companion. The bright biconical structure of the Red Rectangle nebula can be understood to be composed of a multiple double-ring system. In the proposed shaping process, one among several processes through which a companion can shape the circumbinary gas, the companion accretes mass from the slow wind blown by the evolved mass losing star. An accretion disk is formed, and if mass accretion is larger than a critical value, two jets, or a collimated fast wind (CFW) are blown. If the high mass loss rate duration is long, bipolar lobes are formed. If, on the other hand, mass loss rate is intermittent, and during one orbital period the slow wind fills a region which does not extend much beyond the binary system, then only a fraction of the double-lobe structure is formed, namely, rings. This, I propose, was the case with the progenitor of the Red Rectangle, where intermittent episodes of enhanced mass loss rate led to the formation of a multiple double-ring system. 
Noam Soker (Technion, Israel)