在垂死恒星周围形成赤道环
Forming equatorial rings around dying stars
摘要：
我们认为，在演化的巨星周围，如超新星1987 A和项链行星状星云，密集的流出赤道环是由双极喷流形成的，这些喷流将气体压缩到赤道平面。这些喷流是从围绕着恒星伴星的吸积盘中发射出来的。使用FLASH流体动力学数值代码，我们进行3D数值模拟，并表明，双极射流膨胀成致密的球壳可以压缩气体向赤道面，并导致形成一个扩大的赤道环。在相互作用区域的瑞利-泰勒不稳定性打破环块。在大质量恒星和行星状星云中存在相同的环形成机制的假设下，我们发现这种机制比通过第二拉格朗日点的质量损失更有希望形成环。喷流也解释了伴随着许多环的双极星云的存在。
英文摘要：
We suggest that clumpy-dense outflowing equatorial rings around evolved giant stars, such as in supernova 1987A and the Necklace planetary nebula, are formed by bipolar jets that compress gas toward the equatorial plane. The jets are launched from an accretion disk around a stellar companion. Using the FLASH hydrodynamics numerical code we perform 3D numerical simulations, and show that bipolar jets expanding into a dense spherical shell can compress gas toward the equatorial plane and lead to the formation of an expanding equatorial ring. Rayleigh-Taylor instabilities in the interaction region break the ring to clumps. Under the assumption that the same ring-formation mechanism operates in massive stars and in planetary nebulae, we find this mechanism to be more promising for ring formation than mass loss through the second Lagrangian point. The jets account also for the presence of a bipolar nebula accompanying many of the rings.
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