We propose a compact binary model with an eccentric orbit to explain periodically active fast radio burst (FRB) sources, where the system consists of a neutron star (NS) with strong dipolar magnetic fields and a magnetic white dwarf (WD). In our model, the WD fills its Roche lobe at periastron, and mass transfer occurs from the WD to the NS around this point. The accreted material may be fragmented into a number of parts, which arrive at the NS at different times. The fragmented magnetized material may trigger magnetic reconnection near the NS surface. The electrons can be accelerated to an ultra-relativistic speed, and therefore the curvature radiation of the electrons can account for the burst activity. In this scenario, the duty cycle of burst activity is related to the orbital period of the binary. We show that such a model may work for duty cycles roughly from ten minutes to two days. For the recently reported 16.35-day periodicity of FRB 180916.J0158+65, our model does not naturally explain such a long duty cycle, since an extremely high eccentricity ($e>0.95$) is required.

中文翻译：

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周期性活跃快速射电暴源的中子星-白矮星双星模型

我们提出了一个带有偏心轨道的紧凑双星模型来解释周期性活跃的快速射电暴 (FRB) 源，其中系统由具有强偶极磁场的中子星 (NS) 和磁性白矮星 (WD) 组成。在我们的模型中，WD 在 periastron 处填充其 Roche 叶，在这一点附近发生从 WD 到 NS 的质量转移。吸积的物质可能会分裂成许多部分，这些部分在不同的时间到达 NS。破碎的磁化材料可能会触发 NS 表面附近的磁重联。电子可以加速到超相对论速度，因此电子的曲率辐射可以解释爆发活动。在这种情况下，突发活动的占空比与双星的轨道周期有关。我们表明，这样的模型可能适用于大约十分钟到两天的工作周期。对于最近报道的 FRB 180916.J0158+65 的 16.35 天周期，我们的模型并不能自然地解释如此长的占空比，因为需要极高的偏心率（$e>0.95$）。