We present the first Southern-Hemisphere all-sky imager and radio-transient monitoring system implemented on two prototype stations of the low-frequency component of the Square Kilometre Array (SKA-Low). Since its deployment, the system has been used for real-time monitoring of the recorded commissioning data. Additionally, a transient searching algorithm has been executed on the resulting all-sky images. It uses a difference imaging technique to enable identification of a wide variety of transient classes, ranging from human-made radio-frequency interference to genuine astrophysical events. Observations at the frequency 159.375 MHz and higher in a single coarse channel ( $\approx$ 0.926 MHz) were made with 2 s time resolution, and multiple nights were analysed generating thousands of images. Despite having modest sensitivity ( $\sim$ few Jy beam–1), using a single coarse channel and 2-s imaging, the system was able to detect multiple bright transients from PSR B0950+08, proving that it can be used to detect bright transients of an astrophysical origin. The unusual, extreme activity of the pulsar PSR B0950+08 (maximum flux density $\sim$ 155 Jy beam–1) was initially detected in a ‘blind’ search in the 2020 April 10/11 data and later assigned to this specific pulsar. The limitations of our data, however, prevent us from making firm conclusions of the effect being due to a combination of refractive and diffractive scintillation or intrinsic emission mechanisms. The system can routinely collect data over many days without interruptions; the large amount of recorded data at 159.375 and 229.6875 MHz allowed us to determine a preliminary transient surface density upper limit of $1.32 \times 10^{-9} \text{deg}^{-2}$ for a timescale and limiting flux density of 2 s and 42 Jy, respectively. In the future, we plan to extend the observing bandwidth to tens of MHz and improve time resolution to tens of milliseconds in order to increase the sensitivity and enable detections of fast radio bursts below 300 MHz.

中文翻译：

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用于 SKA-Low 原型站的南半球全天无线电瞬态监测器

我们展示了在平方公里阵列 (SKA-Low) 低频分量的两个原型站上实施的第一个南半球全天成像仪和无线电瞬态监测系统。自部署以来，该系统一直用于对记录的调试数据进行实时监控。此外，对生成的全天空图像执行了瞬态搜索算法。它使用差异成像技术来识别各种瞬态类别，从人为的射频干扰到真正的天体物理事件。在单个粗信道（ $\约$ 0.926 MHz）以 2 秒的时间分辨率制作，并分析了多个夜晚，生成了数千张图像。尽管有适度的敏感性（ $\sim$ 几Jy梁–1)，使用单个粗通道和 2 秒成像，该系统能够检测到来自 PSR B0950+08 的多个明亮瞬变，证明它可用于检测天体物理起源的明亮瞬变。脉冲星 PSR B0950+08 异常的极端活动（最大通量密度 $\sim$ 155 焦梁–1) 最初是在 2020 年 4 月 10/11 数据中的“盲”搜索中发现的，后来被分配给这个特定的脉冲星。然而，我们数据的局限性使我们无法对这种效应是由折射和衍射闪烁或固有发射机制的组合做出确切的结论。系统可以连续多日定期收集数据而不会中断；在 159.375 和 229.6875 MHz 处记录的大量数据使我们能够确定初步的瞬态表面密度上限 $1.32 \times 10^{-9} \text{deg}^{-2}$ 时间尺度和限制通量密度分别为 2 s 和 42 Jy。未来，我们计划将观测带宽扩展到数十兆赫兹，并将时间分辨率提高到数十毫秒，以提高灵敏度并实现对300兆赫以下快速无线电突发的探测。