缺失硬态和规则爆发：候选黑洞4U 1630-472的令人费解的情况
Missing hard states and regular outbursts: the puzzling case of the black hole candidate 4U 1630-472
摘要：
4U 1630-472是一个周期性的X射线瞬变，根据其光谱和时间特性被归类为黑洞候选者。这个源的特点之一是存在定期爆发，复发周期在600和730天之间，自1969年发现该源以来一直观察到。我们报告的光谱和时序行为的比较研究发生在2006年，2008年和2010年的三个连续爆发。我们分析了国际伽马射线天体物理实验室（INTEGRAL）和罗西X射线计时探测器（RXTE）在这三年的活动中收集的所有数据。我们发现，尽管有一个类似的光谱和定时行为的能量范围在3和30千电子伏之间，这三个爆发显示出明显的差异超过30千电子伏。事实上，2010年爆发在高能量下延伸，直到150-200 keV没有任何可检测的截止，而2006年和2008年发生的前两次爆发在30 keV以上根本没有检测到。因此，尽管一个非常相似的吸积盘的演变，这三个爆发表现出完全不同的康普顿电子日冕的特性，显示出软化的演变很少观察到之前在低质量的X射线二进制主机的黑洞。我们认为，未知的扰动，导致的爆发是等距的时间可能是这种特殊行为的起源。最后，我们描述了几种可能的情况，可以解释爆发的规律性，确定最合理的，如第三个机构围绕双星系统的轨道。
英文摘要：
4U 1630-472 is a recurrent X-ray transient classified as a black-hole candidate from its spectral and timing properties. One of the peculiarities of this source is the presence of regular outbursts with a recurrence period between 600 and 730 d that has been observed since the discovery of the source in 1969. We report on a comparative study on the spectral and timing behaviour of three consecutive outbursts occurred in 2006, 2008 and 2010. We analysed all the data collected by the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) and the Rossi X-ray timing Explorer (RXTE) during these three years of activity. We show that, in spite of having a similar spectral and timing behaviour in the energy range between 3 and 30 keV, these three outbursts show pronounced differences above 30 keV. In fact, the 2010 outburst extends at high energies without any detectable cut-off until 150-200 keV, while the two previous outbursts that occurred in 2006 and 2008 are not detected at all above 30 keV. Thus, in spite of a very similar accretion disk evolution, these three outbursts exhibit totally different characteristics of the Compton electron corona, showing a softening in their evolution rarely observed before in a low mass X-ray binary hosting a black hole. We argue the possibility that the unknown perturbation that causes the outbursts to be equally spaced in time could be at the origin of this particular behaviour. Finally we describe several possible scenarios that could explain the regularity of the outbursts, identifying the most plausible, such as a third body orbiting around the binary system.
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