来自大质量恒星的高能发射：2009年1月极小期后船底座伊塔星的早熟X射线恢复
High energy emission from massive stars: the precocious X-Ray recovery of Eta Carinae after January 2009 minimum
摘要：
2008年12月15日至2009年3月11日期间，我们利用Swift卫星上的X射线望远镜，在0.3-10 keV能量范围内观测了船底座Eta双星系统，即X射线从最大值下降到最小值的前1个月到后2个月，认为这与主星与热伴星的近星相遇有关。从日食前几个月开始，两颗恒星风之间的相互作用加剧，X射线通量达到最大。此后，通量急剧下降，在大约20天内下降到比“高状态”低至少10倍的水平，即在其5.52年轨道的最大部分（~e-11 erg/s/cm 2）期间系统的X射线发射状态。与之前的周期不同，当低状态持续约2.5个月时，RXTE的观察表明，X射线通量在最小值后约1.5个月开始恢复到正常水平。我们认为，这种早期恢复可能是由于伴随风在遇到激波之前就达到了终极速度。
英文摘要：
We observed the massive binary stellar system of Eta Carinae in the 0.3-10 keV energy range with the X-ray Telescope onboard the Swift satellite during the period 15 December 2008 - 11 March 2009, i.e. 1 month before to 2 months after the X-ray drop from maximum to minimum, thought to be associated with the periastron encounter of the primary star by the hot companion. Beginning a few months before eclipse, the interaction between the winds of the two stars intensifies and the X-ray flux reaches maximum. The flux drops dramatically thereafter, subsiding in about 20 days to a level that is at least a factor 10 lower than the 'high state', i.e. the X-ray emission state of the system during the largest fraction of its 5.52 yr orbit (~e-11 erg/s/cm2). Unlike in previous cycles, when the low state lasted about 2.5 months, observations with RXTE showed that the X-ray flux started its recovery to normal level about 1.5 months after the minimum. We suggest that this early recovery may be due to the fact that the companion wind reaches terminal velocity before encountering the shock.
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