用袖珍关联函数实现射电瞬变的毫秒成像
Millisecond Imaging of Radio Transients with the Pocket Correlator
摘要：
我们展示了一个信号处理的概念，成像的天空在毫秒速率与无线电干涉仪。“袖珍关联函数”（PoCo）将来自无线电干涉仪的多个元件的信号关联起来，速度足够快，可以对短暂的分散脉冲进行成像。根据干涉测量的性质，毫秒关联函数的功能类似于大型单碟望远镜，但具有改进的测量速度，空间定位，校准和干扰抑制。为了测试这个概念，我们在艾伦望远镜阵列（ATA）上安装了PoCo，使用总功率，基于可分辨性和图像平面技术搜索蟹状星云脉冲星B 0329 +54和M31的分散脉冲。在1.7小时的观测中，PoCo探测到了来自蟹状星云脉冲星的191个巨脉冲，其亮度超过了典型的5 sigma灵敏度极限60 Jy，脉冲宽度为3毫秒。大约40%的脉冲星B 0329 +54的脉冲是通过使用新的基于能力的技术检测到的。M31的观测将星系周围3度区域中亮度超过190 Jy的脉冲速率限制为<4.3/hr. We计算了各种基于概率的脉冲搜索算法的计算需求，并演示了计算集群如何帮助满足这一需求。快速成像概念的更大实现将在我们的银河系及更远的地方进行毫秒脉冲的盲搜索，为星际/星系间介质提供有价值的探测，发现新的无线电瞬变，并将其定位以限制其起源的模型。
英文摘要：
We demonstrate a signal processing concept for imaging the sky at millisecond rates with radio interferometers. The "Pocket Correlator" (PoCo) correlates the signals from multiple elements of a radio interferometer fast enough to image brief, dispersed pulses. By the nature of interferometry, a millisecond correlator functions like a large, single-dish telescope, but with improved survey speed, spatial localization, calibration, and interference rejection. To test the concept, we installed PoCo at the Allen Telescope Array (ATA) to search for dispersed pulses from the Crab pulsar, B0329+54, and M31 using total-power, visibility-based, and image-plane techniques. In 1.7 hours of observing, PoCo detected 191 giant pulses from the Crab pulsar brighter than a typical 5 sigma sensitivity limit of 60 Jy over pulse widths of 3 milliseconds. Roughly 40% of pulses from pulsar B0329+54 were detected by using novel visibility-based techniques. Observations of M31 constrain the rate of pulses brighter than 190 Jy in a three degree region surrounding the galaxy to <4.3/hr. We calculate the computational demand of various visibility-based pulse search algorithms and demonstrate how compute clusters can help meet this demand. Larger implementations of the fast imaging concept will conduct blind searches for millisecond pulses in our Galaxy and beyond, providing a valuable probe of the interstellar/intergalactic media, discovering new kinds of radio transients, and localizing them to constrain models of their origin.
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