近日，意大利国家天体物理研究院行星际物理研究所的Gabriele Bruni及其研究团队取得一项新进展。经过不懈努力，他们揭示快速射电暴持续射电发射的星云起源。相关研究成果已于2024年8月7日在国际权威学术期刊《自然》上发表。

本文报道了与距离413Mpc的重复快速射电暴源FRB20201124A相关的第三个亮度较低的持续射电源的检测，这一发现显著地将预测的关系扩展到了低光度-低法拉第旋转测量值（<1,000radm^-2）的范围。在法拉第旋转测量值较低的情况下，预期的射电光度会低于当今射电望远镜的检测阈值极限。

这些发现支持了这样一个观点：迄今为止观测到的持续射电源是由快速射电暴环境中的星云产生的，并且由于磁离子介质较弱，法拉第旋转测量值较低的快速射电暴可能不会显示出持续射电源。这通常与以年轻磁星作为快速射电暴中央引擎的模型相一致，在该模型中，周围的电离星云或双星系统中的相互作用激波为持续射电源提供能量。

据悉，快速射电暴（FRBs）是持续时间仅为毫秒、亮度极高（约Jy）的河外射电暴，但其产生机制尚不清楚。最近，发现两个重复出现的FRBs与一个物理上相关联的非热起源持续射电源有关。这两个FRBs的法拉第旋转测量值异常大，可能追踪到一个密集的磁离子介质，这与源自FRB源周围星云的同步辐射相一致。最近的理论认为，如果观测到的法拉第旋转测量值主要来自持续射电源区域，那么持续射电源的光度和旋转测量值本身之间应该存在简单的关系。

附：英文原文

Title: A nebular origin for the persistent radio emission of fast radio bursts

Author: Bruni, Gabriele, Piro, Luigi, Yang, Yuan-Pei, Quai, Salvatore, Zhang, Bing, Palazzi, Eliana, Nicastro, Luciano, Feruglio, Chiara, Tripodi, Roberta, OConnor, Brendan, Gardini, Angela, Savaglio, Sandra, Rossi, Andrea, Nicuesa Guelbenzu, Ana M., Paladino, Rosita

Issue&Volume: 2024-08-07

Abstract: Fast radio bursts (FRBs) are millisecond-duration, bright (approximately Jy) extragalactic bursts, whose production mechanism is still unclear. Recently, two repeating FRBs were found to have a physically associated persistent radio source of non-thermal origin. These two FRBs have unusually large Faraday rotation measure values, probably tracing a dense magneto-ionic medium, consistent with synchrotron radiation originating from a nebula surrounding the FRB source. Recent theoretical arguments predict that, if the observed Faraday rotation measure mostly arises from the persistent radio source region, there should be a simple relation between the persistent radio source luminosity and the rotation measure itself. Here we report the detection of a third, less luminous persistent radio source associated with the repeating FRB source FRB20201124A at a distance of 413Mpc, substantially expanding the predicted relation into the low luminosity–low Faraday rotation measure regime (<1,000radm^-2). At lower values of the Faraday rotation measure, the expected radio luminosity falls below the limit-of-detection threshold for present-day radio telescopes. These findings support the idea that the persistent radio sources observed so far are generated by a nebula in the FRB environment and that FRBs with low Faraday rotation measure may not show a persistent radio source because of a weaker magneto-ionic medium. This is generally consistent with models invoking a young magnetar as the central engine of the FRB, in which the surrounding ionized nebula—or the interacting shock in a binary system—powers the persistent radio source.

DOI: 10.1038/s41586-024-07782-6

Source: https://www.nature.com/articles/s41586-024-07782-6