Radio observations of Circinus X-1 over a complete orbit at an historically faint epoch
Radio observations of Circinus X-1 over a complete orbit at an historically faint epoch
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圆规座 X-1 在历史上微弱历元的完整轨道上的无线电观测
DOI：
10.1111/j.1365-2966.2011.19708.x
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发表时间：
2011
影响因子：
4.8
通讯作者：
M. Bell
中科院分区：
文献类型：
--
作者：
D. Calvelo;R. Fender;A. Tzioumis;N. Kawai;J. Broderick;M. Bell
我们介绍了使用澳大利亚望远镜紧凑型阵列宽带后端对中子星X射线双星圆盘X-1的完整轨道(∼17和d)进行首次射电观测的结果，这是在该系统处于历史上较暗的状态时拍摄的。我们捕捉到了一个近地天体通道耀斑的快速起伏，事件前9天的通量密度稳定在5.5千兆赫的∼1 MJy和9 GHz的∼0.5MJy。在耀斑下降期间(55206.69 MJD)测量到了5.5千兆赫和9 GHz时的最高通量密度，分别为43.0±0.5MJy和29.9±0.6MJy，并在接下来的6天内继续接近耀斑前的通量密度。对耀斑前数据的成像揭示了稳定的结构，包括在核心15角秒内的两个稳定成分，我们认为这可能是系统外流中的持续发射区，其中一个可能与系统的反喷流有关。与过去在该系统较亮时期进行的观测不同，我们在核心位置的≈3角秒内没有观察到显著的结构变化。模型减去和差异映射为距离核心略远的变化提供了证据：最远可达5角秒。如果与观测到的核心耀斑有关，那么这些变化表明Γ>；35的外流速度非常高，尽管如果我们引用至少一个轨道周期的相位延迟，这种速度可以显著降低。有趣的是，最强烈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。我们讨论了这一行为的含义，包括进动或扭曲的接近喷流的可能性。
We present results from the first radio observations of a complete orbit (∼17 d) 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 d 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 d. Imaging of pre-flare data reveals steady structure including two stable components within 15 arcsec 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 ≈3 arcsec of the core’s position. Model subtraction and difference mapping provide evidence for variations slightly further from the core: up to 5 arcsec 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.