EPIC 216747137 is a new HW~Virginis system discovered by the Kepler spacecraft during its K2 "second life". Like the other HW Vir systems, EPIC 216747137 is a post-common-envelope eclipsing binary consisting of a hot subluminous star and a cool low-mass companion. The short orbital period of 3.87 hours produces a strong reflection effect from the secondary (~9% in the R band). Together with AA Dor and V1828 Aql, EPIC 216747137 belongs to a small subgroup of HW Vir systems with a hot evolved sdOB primary. We find the following atmospheric parameters for the hot component: Teff=40400$\pm$1000 K, logg=5.56$\pm$0.06, log(N(He)/N(H))=$-$2.59$\pm$0.05. The sdOB rotational velocity vsini=51$\pm$10 km/s implies that the stellar rotation is slower than the orbital revolution and the system is not synchronized. When we combine photometric and spectroscopic results with the Gaia parallax, the best solution for the system corresponds to a primary with a mass of about 0.62 Msun close to, and likely beyond, the central helium exhaustion, while the cool M-dwarf companion has a mass of about 0.11 Msun.

中文翻译：

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EPIC 216747137：一个新的 HW Vir 日食二进制文件，带有一个巨大的 sdOB 主星和一个低质量的 M 矮星伴星

EPIC 216747137 是开普勒宇宙飞船在其 K2“第二次生命”期间发现的新 HW~Virginis 系统。与其他 HW Vir 系统一样，EPIC 216747137 是一个后公共包络食双星，由一颗炽热的亚光亮恒星和一颗凉爽的低质量伴星组成。3.87 小时的短轨道周期产生了来自次级的强烈反射效应（R 波段约为 9%）。与 AA Dor 和 V1828 Aql 一起，EPIC 216747137 属于 HW Vir 系统的一个小子组，具有热演化的 sdOB 主系统。我们发现热分量的以下大气参数：Teff=40400$\pm$1000 K，logg=5.56$\pm$0.06，log(N(He)/N(H))=$-$2.59$\pm$0.05。sdOB 旋转速度 vsini=51$\pm$10 km/s 意味着恒星自转比轨道公转慢，系统不同步。