标题： 大质量恒星的高能辐射：2009年1月最小值后Eta Carinae的早熟X射线恢复 显示英文标题

标题： High energy emission from massive stars: the precocious X-Ray recovery of Eta Carinae after January 2009 minimum

摘要： 我们利用Swift卫星上的X射线望远镜在0.3-10 keV能段对η卡罗二元星系统进行了观测，时间范围为2008年12月15日至2009年3月11日，即从最大值到最小值的X射线下降前一个月到下降后两个月，据认为这一下降与主星与炽热伴星的近日点相遇有关。 在掩食开始前几个月，两颗恒星风之间的相互作用增强，X射线通量达到最大值。 此后通量急剧下降，在大约20天内降至‘高态’以下至少一个数量级的水平，即系统在其5.52年轨道（约~10^-11 erg/s/cm²）的大约5/6时间内所处的X射线发射状态。 与之前的周期不同，当时低态持续了约2.5个月，RXTE的观测显示，X射线通量在最低点之后约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星风在遇到冲击波之前就已经达到了终端速度。 显示英文摘要

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.