Possible regular phenomena in EXO 2030+375
Possible regular phenomena in EXO 2030+375
复制标题
EXO 2030 375中可能出现的规律现象
DOI：
10.1051/0004-6361/201629373
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发表时间：
2017
影响因子：
6.5
通讯作者：
Andrea
中科院分区：
文献类型：
--
作者：
Laplace;Eva; Mihara;Tatehiro; Moritani;Yuki; Nakajima;Motoki; Takagi;Toshihiro; Makishima;Kazuo; Santangelo;Andrea
在过去的10年里，自2006年的最后一次巨大爆发以来，在Be X射线双星EXO 2030+375的每一次近星点通过中都检测到了规则的X射线爆发（I型）。然而，最近有报道称，该源开始表现出一种特殊的行为：它的X射线通量显着下降，并且在几种情况下错过了I型爆发。与此同时，中子星星的自旋频率，自2006年巨大爆发结束以来一直在稳步增加，达到了一个平台。最近的观测表明，源现在开始自旋下降。这些观测到的现象与21年前发生的现象有着惊人的相似之处，就在源显示出爆发峰值的突然轨道相移之前（1995年）。这一历史事件发生在两次大爆发（1985年和2006年）之间。这些现象表明该系统在轨道相移和/或巨爆发之间有10.5年的潜在周期性。所提出的周期性可能反映了Be星星的拱星盘中的一些长周期动力学，例如，Kozai-Lidov效应。一个模型产生这样的周期性变化的Be盘，即Kozai-Lidov振荡的Be盘，进行了讨论。如果这种行为真的是周期性的，那么另一个X射线爆发峰值的相移预计将在2016年12月左右发生。
In the last 10 yr, since its last giant outburst in 2006, regular X-ray outbursts (type I) were detected every periastron passage in the Be X-ray binary EXO 2030+375. Recently, however, it was reported that the source started to show a peculiar behavior: its X-ray flux decreased significantly and type I outbursts were missed in several cases. At the same time, the spin frequency of the neutron star, which had been increasing steadily since the end of the 2006 giant outburst, reached a plateau. Very recent observations indicate that the source is now starting to spin down. These observed phenomena have a striking similarity with those which took place 21 yr ago, just before the source displayed a sudden orbital phase shift of the outburst peak (1995). This historical event occurred at the time exactly between the two giant outbursts (1985 and 2006). These phenomena suggest the system to have an underlying periodicity of 10.5 yr between orbital phase shifts and/or giant outbursts. The suggested periodicity may reflect some long-period dynamics in the circumstellar disk of the Be star, due, e.g., to the Kozai-Lidov effect. A model generating such a periodic change of the Be disk, namely Kozai-Lidov oscillations in the Be disk, is discussed. If this behavior is really periodical, another phase shift of the X-ray outburst peak is predicted to occur around 2016 December.