利用MeerTRAP瞬态缓冲系统对两个低偏振分量快速射电暴的定位研究
A study of two FRBs with low polarization fractions localized with the MeerTRAP transient buffer system
AI总结：
本文利用MeerTRAP瞬态缓冲系统对两个快速射电暴实现约1角秒精度定位，识别出其中一个的宿主星系，并分析其低偏振、色散量和散射特性，揭示了宿主星系等离子体环境对观测性质的影响。
摘要：
将快速射电暴（FRBs）定位到角秒和亚角秒精度，可以最大限度地发挥其作为宇宙学探针的潜力。为此，FRB探测设备正在部署触发式复电压捕获系统，以定位FRB、识别其宿主星系并测量红移。本文报告了两个FRB（20220717A和20220905A）的发现与定位，它们由南非MeerKAT望远镜上MeerTRAP仪器部署的瞬态缓冲系统捕获。我们能够将这两个FRB定位到约1角秒的精度，从而能够明确识别FRB 20220717A的宿主星系（后验概率约为0.97）。FRB 20220905A位于天空中一个拥挤的区域，其宿主星系仅有尝试性识别，但由于目标暗淡以及难以获得光谱，无法建立确定的关联。这两个爆发表现出较低的线偏振分量（10--17%），这与在明显非重复的FRB中观测到的偏振分量多样性一致，类似于中子星的单脉冲。我们还表明，FRB 20220717A的宿主星系贡献了总色散量（DM）的大约15%，表明它位于宿主星系中富含等离子体的区域，这可以解释其较大的旋转量。FRB 20220717A中的散射主要可归因于宿主星系和介入介质，并且与更广泛的FRB群体中所观测到的现象一致。
英文摘要：
Localisation of fast radio bursts (FRBs) to arcsecond and sub-arcsecond precision maximizes their potential as cosmological probes. To that end, FRB detection instruments are deploying triggered complex-voltage capture systems to localize FRBs, identify their host galaxy and measure a redshift. Here, we report the discovery and localisation of two FRBs (20220717A and 20220905A) that were captured by the transient buffer system deployed by the MeerTRAP instrument at the MeerKAT telescope in South Africa. We were able to localize the FRBs to a precision of $\sim$1 arc-second that allowed us to unambiguously identify the host galaxy for FRB 20220717A (posterior probability$\sim$0.97). FRB 20220905A lies in a crowded region of the sky with a tentative identification of a host galaxy but the faintness and the difficulty in obtaining an optical spectrum preclude a conclusive association. The bursts show low linear polarization fractions (10--17$\%$) that conform to the large diversity in the polarization fraction observed in apparently non-repeating FRBs akin to single pulses from neutron stars. We also show that the host galaxy of FRB 20220717A contributes roughly 15$\%$ of the total dispersion measure (DM), indicating that it is located in a plasma-rich part of the host galaxy which can explain the large rotation measure. The scattering in FRB 20220717A can be mostly attributed to the host galaxy and the intervening medium and is consistent with what is seen in the wider FRB population.
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