Unseen companions of V Hya inferred from periodic ejections
Unseen companions of V Hya inferred from periodic ejections
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DOI：
10.1093/mnras/stz1515
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发表时间：
2019-02
影响因子：
4.8
通讯作者：
J. Salas;S. Naoz;M. Morris;A. Stephan
中科院分区：
文献类型：
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作者：
J. Salas;S. Naoz;M. Morris;A. Stephan
最近一项利用哈勃太空望远镜观测的研究发现，星星V Hya存在周期性、高速、准直的喷射（或称“子弹”）。该研究的作者提出了一个模型，将这些子弹与一个看不见的亚恒星伴星的近星通过联系起来，该伴星在偏心轨道上运行，轨道周期为2.8年。在这里，我们提出V Hya是一个三重系统的一部分，其中一个亚恒星伴星的轨道周期为108年，而第三个天体的轨道要宽得多。在这个模型中，更遥远的物体通过偏心Kozai-Lidov机制在亚恒星伴星的轨道上引起高偏心率激发。这些偏心率可以达到如此高的值，它们导致罗奇瓣交叉，通过强烈增强的吸积情节产生所观察到的子弹喷射。例如，我们发现，一个弹道子弹弹射机制可以产生一个棕矮星质量的同伴，而磁驱动的外流是一致的木星质量的同伴。最后，我们认为，遥远的同伴可能居住在几百个天文单位的偏心轨道上。
A recent study using Hubble Space Telescope observations found periodic, high-speed, collimated ejections (or ‘bullets’) from the star V Hya. The authors of that study proposed a model associating these bullets with the periastron passage of an unseen, substellar companion in an eccentric orbit and with an orbital period of ∼8 yr. Here we propose that V Hya is part of a triple system, with a substellar companion having an orbital period of ∼8 yr, and a tertiary object on a much wider orbit. In this model, the more distant object causes high-eccentricity excitations on the substellar companion’s orbit via the Eccentric Kozai–Lidov mechanism. These eccentricities can reach such high values that they lead to Roche-lobe crossing, producing the observed bullet ejections via a strongly enhanced accretion episode. For example, we find that a ballistic bullet ejection mechanism can be produced by a brown-dwarf-mass companion, while magnetically driven outflows are consistent with a Jovian-mass companion. Finally, we suggest that the distant companion may reside at few a hundred astronomical units on an eccentric orbit.