孤儿原恒星
Orphaned Protostars
摘要：
我们探讨了一个遥远的同伴（~1000 - 5000 AU）的人口的起源，I类原恒星源最近发现的康奈利和同事，谁指出，随着源的演变，同伴的分数减少。在这里，我们提出了N体模拟嵌入在稠密的云核不稳定的三重系统。许多伴星被弹射到未束缚的轨道并迅速逃逸，但其他伴星被弹射出来的动量不足，无法爬出云核和相关双星的势阱。这些松散结合的伴星到达数千天文单位的距离，然后回落，最终随着云核逐渐消失而被弹射出去。我们用孤儿这个词来表示原恒星物体，它们从胎盘云核中动态地喷射出来，要么逃逸，要么暂时以大的距离微弱地束缚在一起。所有的三重系统中有一半被发现在原恒星阶段解体，所以如果多个系统是云核崩溃的常见结果，那么孤儿应该是常见的。绑定孤儿与嵌入密切的原恒星双星，但逃脱孤儿可以旅行远至~0.2 pc在原恒星阶段。从一个潜在的井中陡峭地爬出来，确保了孤儿星在运动学上与出生时没有那么暴力的前历史的年轻恒星没有区别。在它们的重对流云核之外识别孤儿将允许在近红外，在某些情况下甚至在光学波长上详细研究Hayashi轨道上的原恒星。
英文摘要：
We explore the origin of a population of distant companions (~1000 - 5000 AU) to Class I protostellar sources recently found by Connelley and co-workers, who noted that the companion fraction diminished as the sources evolved. Here we present N-body simulations of unstable triple systems embedded in dense cloud cores. Many companions are ejected into unbound orbits and quickly escape, but others are ejected with insufficient momentum to climb out of the potential well of the cloud core and associated binary. These loosely bound companions reach distances of many thousands of AU before falling back and eventually being ejected into escapes as the cloud cores gradually disappear. We use the term orphans to denote protostellar objects that are dynamically ejected from their placental cloud cores, either escaping or for a time being tenuously bound at large separations. Half of all triple systems are found to disintegrate during the protostellar stage, so if multiple systems are a frequent outcome of the collapse of a cloud core, then orphans should be common. Bound orphans are associated with embedded close protostellar binaries, but escaping orphans can travel as far as ~0.2 pc during the protostellar phase. The steep climb out of a potential well ensures that orphans are not kinematically distinct from young stars born with a less violent pre-history. The identification of orphans outside their heavily extincted cloud cores will allow the detailed study of protostars high up on their Hayashi tracks at near-infrared and in some cases even at optical wavelengths.
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