Circinus X-1在一个完整轨道上的历史弱时期的射电观测
Radio observations of Circinus X-1 over a complete orbit at an historically faint epoch
摘要：
我们目前的结果，从第一个完整的轨道（~ 17天）的中子星X射线双星Circinus X-1使用澳大利亚望远镜紧凑阵列宽带后端，而系统是在一个历史上微弱的状态。我们已经捕获到了一个近星通道耀斑的快速上升和下降，事件发生前9天的通量密度在5.5 GHz稳定在~ 1 mJy，在9 GHz稳定在~ 0.5 mJy。最高通量密度为43.0 +/- 0.5 mJy（5.5 GHz）和29.9 +/- 0.6 mJy（9 GHz）是在耀斑下降期间测得的（MJD 55206.69），在接下来的6天内继续向耀斑前通量密度发展。耀斑前数据的成像揭示了稳定的结构，包括两个稳定的组成部分，在15弧秒的核心，我们认为可能是持续的排放区域内的系统的流出，其中之一是可能与系统的反喷流。与过去在系统较亮时期进行的观测不同，我们在核心位置的\approx 3弧秒内没有观察到显著的结构变化。模型减法和差分映射提供了距离核心稍远的变化的证据：最多5”。如果与观测到的核心耀斑有关，那么这些变化表明非常高的外流速度，Γ > 35，尽管如果我们调用至少一个轨道周期的相位延迟，这可以显着降低。有趣的是，最强的结构变化出现在核心的西北部，与历史上最强的弧秒尺度发射相反。我们讨论了这种行为的影响，包括可能的进动或扭结接近喷气。
英文摘要：
We present results from the first radio observations of a complete orbit (~ 17 days) of the neutron star X-ray binary Circinus X-1 using the Australia Telescope Compact Array Broadband Backend, taken while the system was in an historically faint state. We have captured the rapid rise and decline of a periastron passage flare, with flux densities for 9 days prior to the event stable at ~ 1 mJy at 5.5 GHz and ~ 0.5 mJy at 9 GHz. The highest flux densities of 43.0 +/- 0.5 mJy at 5.5 GHz and 29.9 +/- 0.6 mJy at 9 GHz were measured during the flare's decline (MJD 55206.69) which continues towards pre-flare flux densities over the following 6 days. Imaging of pre-flare data reveals steady structure including two stable components within 15 arc-seconds of the core which we believe may be persistent emission regions within the system's outflows, one of which is likely associated with the system's counter-jet. Unlike past observations carried out in the system's brighter epochs, we observe no significant structural variations within \approx 3 arc-seconds of the core's position. Model subtraction and difference mapping provide evidence for variations slightly further from the core: up to 5" away. If related to the observed core flare, then these variations suggest very high outflow velocities with Γ > 35, though this can be reduced significantly if we invoke phase delays of at least one orbital period. Interestingly, the strongest structural variations appear to the north west of the core, opposite to the strongest arcsec-scale emission historically. We discuss the implications of this behaviour, including the possibility of precession or a kinked approaching jet.
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