多周期场SX Phe型脉动星BL鹿豹座星的星震学研究
Asteroseismology of the multiperiodic field SX Phe pulsator BL Camelopardalis
中文总结 AI 辅助
本研究以银河系场金属丰度最低的SX Phe型脉动星BL Cam为对象，结合TESS空间数据与ZTF地面观测，采用贝叶斯星震建模确定其参数、脉动特性及双星属性，为贫金属脉动星模型提供了基准。
中文摘要 AI 辅助
BL鹿豹座星（BL Cam）是银河系场中已知金属丰度最低的SX Phoenicis型恒星，是研究星族II恒星结构与演化、探索蓝掉队星形成通道的绝佳试验平台。本研究旨在确定BL Cam的基本恒星参数与脉动特性，并明确其观测到的振荡模式的本质。我们分析了来自TESS任务的高精度空间数据，以及来自兹威基瞬变巡天（ZTF）的长期地面观测数据；其中ZTF数据主要用于推导该系统的轨道参数，而TESS光变曲线使我们能够提取丰富的振荡频谱。我们识别出多个脉动频率，并采用贝叶斯方法开展星震建模。我们检测到大量脉动频率，包括一个主导径向模式和额外的非径向分量，且在星震模型中预测所有拟合模式均被激发。模型重现了两个振幅最高的独立频率（即径向基频和一个偶极模式），并暗示可能存在额外的径向泛音。推断出的恒星参数证实了BL Cam的极低金属丰度，同时确认其为双星系统，轨道周期为144天。BL Cam为测试贫金属脉动星的恒星模型提供了宝贵基准，空间测光与贝叶斯星震建模的结合能够可靠地约束其内部结构与脉动特性。
英文摘要
BL Camelopardalis (BL Cam) is the most metal-poor SX Phoenicis star known in the Galactic field, making it an excellent test bed for studies of Population II stellar structure and evolution, as well as for investigating the formation channels of blue straggler stars. We aim to constrain fundamental stellar parameters and pulsational properties of BL Cam and identify the nature of its observed oscillation modes. We analysed high-precision space-based data from the TESS mission and long-term ground-based observations from the Zwicky Transient Facility (ZTF) survey. The ZTF data were primarily used to derive the orbital parameters of the system, while the TESS light curves enabled us to extract a rich oscillation spectrum. We identified multiple pulsation frequencies and performed seismic modelling using a Bayesian approach. We detected numerous pulsation frequencies, including a dominant radial mode and additional non-radial components. We predicted all fitted modes in our seismic models as excited. The models reproduced the two highest amplitude-independent frequencies (i.e. the radial fundamental mode and a dipole mode) and suggested the possible presence of additional radial overtones. The inferred stellar parameters confirm the extremely low metallicity of BL~Cam. We also confirm its binary nature, with an orbital period of 144 days. BL Cam provides a valuable benchmark for testing stellar models of metal-poor pulsators. The combination of space-based photometry and Bayesian seismic modelling enables robust constraints to be placed on its internal structure and pulsation properties.
