X-ray polarimetry has long been considered the ‘holy grail’ of X-ray astronomy. Fortunately, after a silence of more than 40 years, the field is now rejuvenating. In fact, an X-ray polarimeter onboard a Cube-sat nano-satellite has been recently successfully operated. IXPE, the Imaging X-ray Polarimetry Explorer, will be launched in 2021 while eXTP, containing a larger version of IXPE, is expected to be launched in 2027. Although at present it is difficult to predict the discoveries that, given their exploratory nature, IXPE and eXTP will obtain, the path for a follow-up mission can already be envisaged. In this paper we describe the scientific goals of such a follow-up mission, and present a medium-size mission profile that can accomplish this task.

X射线极化技术长期以来一直被视为X射线天文学的“圣杯”。幸运的是，在沉默了40多年之后，这个领域正在焕发青春。实际上，近来已成功地操作了立方立方体纳米卫星上的X射线旋光仪。IXPE（成像X射线极化仪）将于2021年启动，而包含更大版本IXPE的eXTP有望在2027年启动。尽管目前很难预测发现，但鉴于其探索性， IXPE和eXTP将获得，后续任务的路径已经可以设想。在本文中，我们描述了这种后续任务的科学目标，并提出了可以完成此任务的中型任务简介。