We discuss the interaction of the slow wind blown by an asymptotic giant branch (AGB) star with a collimated fast wind (CFW) blown by its main-sequence or white dwarf companion, at orbital separations in the range of several AU approx< a approx< 200 AU. The CFW results from accretion of the AGB wind into an accretion disk around the companion. The fast wind is collimated by the accretion disk. We argue that such systems are the progenitors of bipolar planetary nebulae and bipolar symbiotic nebulae with a very narrow equatorial waist between the two polar lobes. The CFW wind will form two lobes along the symmetry axis and will further compress the slow wind near the equatorial plane, leading to the formation of a dense slowly expanding ring. Therefore, contrary to the common claim that a dense equatorial ring collimates the bipolar flow, we argue that in the progenitors of very narrow waist bipolar planetary nebulae, the CFW, through its interaction with the slow wind, forms the dense equatorial ring. Only later in the evolution, and after the CFW and slow wind cease, does the mass-losing star leave the AGB and blow a second, more spherical, fast wind. At this stage the flow structure becomes the one that is commonly assumed for bipolar planetary nebulae, i.e., collimation of the fast wind by the dense equatorial material. However, this results in the broadening of the waist in the equatorial plane and cannot by itself account for the presence of very narrow waists or jets. We conduct a population synthesis study of the formation of planetary nebulae in wide binary systems which quantitatively supports the proposed model. The population synthesis code follows the evolution of both stars and their arbitrarily eccentric orbit, including mass loss via stellar winds, for 5 x 10~4 primordial binaries. We show the number of expected systems that blow a CFW is in accord with the number found from observations, to within the many uncertainties involved. Overall, we find that ～ 5% of all planetary nebulae are bipolars with very narrow waists. Our population synthesis not only supports the CFW model but more generally supports the binary model for the formation of bipolar planetary nebulae.
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机译：我们讨论了渐近大分支（AGB）恒星吹出的慢风与其主序列或白矮星伴星所吹准直的快速风（CFW）的相互作用，其轨道间隔在几个AU范围内。 <200澳元。 CFW是由AGB风的积聚到伴侣周围的积聚盘中产生的。快速的风通过吸积盘准直。我们认为，这样的系统是双极行星状星云和双极共生星云的祖先，两个极瓣之间的赤道腰很窄。 CFW风将沿着对称轴形成两个裂片，并将进一步压缩赤道平面附近的慢风，从而导致形成一个密集且缓慢扩张的环。因此，与通常认为稠密的赤道环准直双极流的说法相反，我们认为在极窄腰的双极行星状星云的祖先中，CFW通过其与慢风的相互作用而形成了稠密的赤道环。直到演化的后期，并且在CFW和慢风停止后，这颗质量下降的恒星才离开AGB并吹出第二个球形的快速风。在这一阶段，流动结构成为双极行星状星云通常假定的流动结构，即通过稠密的赤道物质准直快速风。然而，这导致腰部在赤道平面上变宽，并且本身不能解释存在非常窄的腰部或射流。我们进行了广泛的二元系统中行星状星云形成的人口综合研究，定量地支持了所提出的模型。总体合成代码遵循5 x 10〜4个原始双星的恒星及其任意偏心轨道的演化，包括通过恒星风造成的质量损失。我们显示，在涉及许多不确定性的范围内，吹扫CFW的预期系统数量与从观测中发现的数量一致。总体而言，我们发现所有行星状星云中约有5％为双极型，腰部非常狭窄。我们的种群合成不仅支持CFW模型，而且更普遍地支持用于形成双极行星状星云的二元模型。
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