Four planetary nebulae (PNe) are considered to be probable or possible members of Galactic globular clusters (GCs). These are Ps 1 = K648 in M15, GJJC 1 = IRAS 18333-2357 in M22, JaFu 1 in Palomar 6, and JaFu 2 in NGC 6441. In addition to lying close to the host GCs on the sky, these PNe have radial velocities that are consistent, within the errors and stellar velocity dispersions, with cluster membership. The remaining membership criterion is whether the proper motions (PMs) of the central stars are in agreement with those of the host clusters. We have carried out the PM test for all four PNe. Two of the central stars--those of Ps 1 and GJJC 1--have PMs listed in the recent Gaia Data Release 2 (DR2). We updated the PM of the Ps 1 central star to a more precise value using archival Hubble Space Telescope (HST) frames. Both PMs are statistically consistent with cluster membership. For the other two PNe, we used archival HST images to derive the PMs of their nuclei. For JaFu 2, there are HST images at several epochs, and the measured PM of the nucleus is in excellent agreement with that of the host cluster. For JaFu 1 the available archival HST images are less optimal and the results are less conclusive; the measured PM for the central star is marginally consistent with cluster membership, but additional astrometric observations are desirable for a more robust membership test.

中文翻译：

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银河球状星团中四个行星状星云的自运动隶属度测试

四个行星状星云 (PNe) 被认为可能是银河球状星团 (GC) 的成员。它们是 M15 中的 Ps 1 = K648、M22 中的 GJJC 1 = IRAS 18333-2357、Palomar 6 中的 JaFu 1 和 NGC 6441 中的 JaFu 2。除了靠近天空中的宿主 GC 外，这些 PNe 还具有径向速度在误差和恒星速度色散范围内，它们与星团成员是一致的。剩下的隶属标准是中央恒星的自行（PM）是否与宿主星团的自行一致。我们已经对所有四个 PNe 进行了 PM 测试。两个中心恒星——Ps 1 和 GJJC 1 的那些——在最近的盖亚数据发布 2 (DR2) 中列出了 PM。我们使用存档的哈勃太空望远镜 (HST) 帧将 Ps 1 中心恒星的 PM 更新为更精确的值。两个 PM 在统计上都与集群成员资格一致。对于另外两个 PNe，我们使用存档的 HST 图像来推导它们原子核的 PM。对于JaFu 2，有几个时期的HST图像，并且测得的核PM与宿主集群的PM非常吻合。对于 JaFu 1，可用的存档 HST 图像不太理想，结果也不太确定；中央恒星的测量 PM 与星团成员略有一致，但需要额外的天体测量观测，以进行更强大的成员测试。对于 JaFu 1，可用的存档 HST 图像不太理想，结果也不太确定；中央恒星的测量 PM 与星团成员略有一致，但需要额外的天体测量观测，以进行更强大的成员测试。对于 JaFu 1，可用的存档 HST 图像不太理想，结果也不太确定；中央恒星的测量 PM 与星团成员略有一致，但需要额外的天体测量观测，以进行更强大的成员测试。