The radio emission from pulsars can scatter from inhomogeneities in the charged particle distribution in the interstellar medium (ISM) in a process called scintillation. The interference caused by this scattering creates bright peaks in a pulsar’s dynamic spectrum, yielding a characteristic ‘scintillation bandwidth’ that depends on density enhancements in the ISM along the line of sight to the pulsar. Using the vast archival dataset compiled during the Arecibo telescope’s AO327 pulsar survey (carried out from 2010 until the telescope’s demise in 2020), Sofia Sheikh and colleagues extracted 38 bandwidths from 23 pulsars in this way. Surprisingly, nearly all of the measurements were larger than expected based on well-used models of the free electron density within the Galaxy, highlighting the need to regularly update such models.

Sheikh and colleagues found different levels of agreement between the two popular Galactic electron density models NE2001 and YMW16 and their scintillation data, with the NE2001 model providing the best overall fit — although this is not unexpected since the NE2001 training pulsars are included in the dataset, while the majority of the YMW16 pulsars were not. Bandwidths for six pulsars were obtained for the first time.

脉冲星的无线电发射可以在称为闪烁的过程中从星际介质 （ISM） 中带电粒子分布的不均匀性中散射。这种散射引起的干扰会在脉冲星的动态光谱中产生明亮的峰值，从而产生一个特征性的“闪烁带宽”，该带宽取决于 ISM 中沿脉冲星视线的密度增强。利用阿雷西博望远镜的 AO327 脉冲星巡天（从 2010 年开始进行，直到 2020 年望远镜消亡）期间汇编的大量档案数据集，Sofia Sheikh 及其同事以这种方式从 23 颗脉冲星中提取了 38 个带宽。令人惊讶的是，几乎所有的测量值都大于基于银河系内自由电子密度的常用模型的预期，这凸显了定期更新此类模型的必要性。

Sheikh 及其同事发现，两种流行的银河电子密度模型 NE2001 和 YMW16 及其闪烁数据之间存在不同程度的一致性，其中 NE2001 模型提供了最佳的整体拟合——尽管这并不意外，因为 NE2001 训练脉冲星包含在数据集中，而大多数 YMW16 脉冲星则没有。首次获得了 6 颗脉冲星的带宽。