The late B-type star V772 Cas (HD 10260) was previously suspected to be a rare example of a magnetic chemically peculiar star in an eclipsing binary system. Photometric observations of this star obtained by the TESS satellite show clear eclipses with a period of 5.0137 d accompanied by a significant out-of-eclipse variation with the same period. High-resolution spectroscopy reveals V772 Cas to be an SB1 system, with the primary component rotating about a factor two slower than the orbital period and showing chemical peculiarities typical of non-magnetic HgMn chemically peculiar stars. This is only the third eclipsing HgMn star known and, owing to its brightness, is one of the very few eclipsing binaries with chemically peculiar components accessible to detailed follow-up studies. Taking advantage of the photometric and spectroscopic observations available for V772 Cas, we performed modelling of this system with the PHOEBE code. This analysis provided fundamental parameters of the components and demonstrated that the out-of-eclipse brightness variation is explained by the ellipsoidal shape of the evolved, asynchronously rotating primary. This is the first HgMn star for which such variability has been definitively identified.

中文翻译：

---

V772 Cas：食双星中一颗椭圆形的 HgMn 星

晚期 B 型星 V772 Cas (HD 10260) 以前被怀疑是食双星系统中具有磁性化学特征的恒星的罕见例子。由 TESS 卫星获得的这颗恒星的光度观测显示，周期为 5.0137 d 的清晰日食伴随着同期显着的日食变化。高分辨率光谱显示 V772 Cas 是一个 SB1 系统，其主要成分的旋转速度比轨道周期慢两倍，并显示出非磁性 HgMn 化学特性恒星的典型化学特性。这只是已知的第三颗食 HgMn 星，由于它的亮度，它是极少数具有化学特殊成分的食双星之一，可用于详细的后续研究。利用可用于 V772 Cas 的光度和光谱观察，我们使用 PHOEBE 代码对该系统进行了建模。该分析提供了组件的基本参数，并证明日食外亮度变化是由演化的、异步旋转的初级的椭球形状解释的。这是第一颗已明确确定这种变异性的 HgMn 星。