在黑暗中束缚它们：赤道环，B[e]超巨星和双极星云的腰部
And in the Darkness Bind Them: Equatorial Rings, B[e] Supergiants, and the Waists of Bipolar Nebulae
摘要：
我们报告在船底座星云西部发现了两个新的星周环星云。较亮的天体SBW 1类似于一只无眼睑的凝视眼睛，环绕着一颗B1.5 Iab超巨星。它的大小与SN 1987 A周围的内环相同，但SBW 1的低N丰度表明该恒星没有经过RSG阶段。较暗的物体SBW 2是一个更加扭曲的环，富含N，并且有一颗看起来不可见的中央恒星。我们讨论这两个新星云的背景下，周围的环SN 1987 A，Sher 25，HD 168625，RY Scuti，WeBo 1，SuWt 2，和其他人。环的承载者分为两类：五个环围绕着热的超巨星，除了一个已知的双星外，所有的环都是围绕着SN 1987 A的环的碳拷贝。我们提出了这些环和B[e]超巨星之间的联系，其中环在早期的B[e]阶段来自相同的材料。剩下的四个环围绕着演化中的中等质量恒星;这个环的所有成员都是近距离的双星，暗示着双星的相互作用控制着这些环的形成。我们估计银河系中可能还有数千个暗环，但由于选择效应，我们几乎没有意识到它们的存在。质量较低的物体可能是赤道密度增强，经常被用来束缚双极PNe的腰部。
英文摘要：
We report the discovery of two new circumstellar ring nebulae in the western Carina Nebula. The brighter object, SBW1, resembles a lidless staring eye and encircles a B1.5 Iab supergiant. Its size is identical to the inner ring around SN1987A, but SBW1's low N abundance indicates that the star didn't pass through a RSG phase. The fainter object, SBW2, is a more distorted ring, is N-rich, and has a central star that seems to be invisible. We discuss these two new nebulae in context with rings around SN1987A, Sher25, HD168625, RY Scuti, WeBo1, SuWt2, and others. The ring bearers fall into two groups: Five rings surround hot supergiants, and all except for the one known binary are carbon copies of the ring around SN1987A. We propose a link between these rings and B[e] supergiants, where the rings derive from the same material in an earlier B[e] phase. The remaining four rings surround evolved intermediate-mass stars; all members of this ring fellowship are close binaries, hinting that binary interactions govern the forging of such rings. We estimate that there may be several thousand more dark rings in the Galaxy, but we are scarcely aware of their existence due to selection effects. The lower-mass objects might be the equatorial density enhancements often invoked to bind the waists of bipolar PNe.
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