AI 中文总结
研究发现Feige 64双星系统中的富金属BHB星是公共包层演化产生的氦壳燃烧星，为BHB星形成的双星相互作用机制提供了直接观测证据
AI 中文摘要
观测上，蓝水平分支（BHB）星被定义为赫罗图中位于极端蓝水平分支与天琴座RR型变星之间特征区域的热星，多数被认为是被剥离的核心氦燃烧星，但双星相互作用在其形成中的作用仍不明确。本文报告在一个轨道周期为0.82628天的双星系统（Feige 64）中发现一颗富金属BHB星，该系统包含一颗质量为0.35±0.03 M☉的BHB星和一颗质量约为1.26±0.17 M☉的白矮星（WD）。这颗BHB星的有效温度为15524±310 K，光度为39.7±4.1 L☉。恒星演化模型表明，它是通过公共包层通道产生的氦壳燃烧星，保留的富氢包层质量比此前认为的低质量恒星的情况更大。该发现为BHB星形成过程中的双星相互作用提供了直接证据，为解释这一新兴星族提供了新视角。
英文摘要
Observationally, blue horizontal branch (BHB) stars are defined as hot stars occupying a characteristic region between the extreme blue horizontal branch and RR Lyrae variables in the Hertzsprung-Russell diagram. Most of them are interpreted as stripped core-helium-burning stars, but the role of binary interaction in their formation remains unclear. Here, we report the discovery of a metal-rich BHB star in a 0.82628-day binary system (Feige 64) comprising a $0.35\pm0.03\,M_{\odot}$ BHB star and a likely $1.26\pm0.17\,M_{\odot}$ white dwarf (WD). The BHB star has an effective temperature of $15{,}524\pm310$ K and a luminosity of $39.7\pm4.1\,L_{\odot}$. Stellar evolution modelling indicates that it is a helium-shell-burning star produced through the common-envelope channel, retaining a hydrogen-rich envelope that is more massive than previously thought for low-mass stars. This finding provides direct evidence for binary interaction in the formation of BHB stars, offering a fresh perspective on interpreting this emerging population.
