发表机构
Institute for Frontier in Astronomy and Astrophysics, Beijing Normal University; School of Physics and Astronomy, Beijing Normal University（前沿天文学与天体物理研究所，北京师范大学; 物理与天文学院，北京师范大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究提出并合场景解释富碳富氧热亚矮星，通过MESA模拟验证，与观测一致，为这类罕见恒星提供可行形成通道。
AI 中文摘要
富碳和富氧热亚矮星（CO-sdO 星）是富氦热亚矮星中一种极为罕见的子类。近期对 PG 1654+322、PG 1528+025 和 UCAC4 108 的观测揭示了其表面碳和氧的质量分数异常高，这在现有形成场景中难以解释。我们探索涉及 sdB 星的并合是否能为这些天体提供可行的形成通道。利用恒星演化代码 MESA，我们模拟了两种并合通道的并合后演化：两个 sdB 星之间的并合，以及氦白矮星与 sdB 星之间的并合。如果并合过程中发生有效混合，sdB 星核心氦燃烧期间合成的碳和氧可能提供天然的化学库。所得的演化轨迹与观测到的这三颗星的有效温度、表面重力和光度大致一致，暗示其残余质量约为 0.8-1.0 太阳质量。我们的计算表明，涉及 sdB 星的并合可能代表富碳热亚矮星的一种可行形成途径。
英文摘要
Carbon- and oxygen-rich hot subdwarfs (CO-sdO stars) represent an extremely rare subclass of helium-rich hot subdwarfs. Recent observations of PG 1654+322, PG 1528+025, and UCAC4 108 reveal unusually large surface mass fractions of carbon and oxygen, which are difficult to explain within existing formation scenarios. We explore whether mergers involving sdB stars can provide a viable formation channel for these objects. Using the stellar evolution code MESA, we model the post-merger evolution of two merger channels: mergers between two sdB stars and mergers between a helium white dwarf and an sdB star. Carbon and oxygen synthesized during core helium burning in sdB stars may provide a natural chemical reservoir if efficient mixing occurs during the merger. The resulting evolutionary tracks are broadly consistent with the effective temperatures, surface gravities, and luminosities observed for the three stars, suggesting remnant masses of about 0.8-1.0 M_sun. Our calculations suggest that mergers involving sdB stars may represent a viable formation pathway for CO-rich hot subdwarfs.
CommentsAccepted for publication in MNRAS. 13 pages, 17 figures
