CoBiToM项目. III. 潜在并合候选体AL Lep、ASAS J082243+1927.0和ZZ PsA的物理表征
CoBiToM project. III. Physical characterisation of the potential merger candidates AL Lep, ASAS J082243+1927.0, and ZZ PsA
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中文总结 AI 辅助
本研究针对CoBiToM项目中的3个潜在并合相接双星AL Lep等，结合VLT/UVES光谱与光变曲线建模，推导其参数，评估演化状态，发现ZZ PsA或处于不稳定演化阶段。
中文摘要 AI 辅助
相接双星（Contact binaries, CBs）是研究可能导致恒星并合的晚期演化阶段的关键系统。质量比极低且填充因子极高的系统尤其受关注，因为它们是潜在的并合候选体，也是发光红新星的可能前身星。本文对相接双星系统AL Lep、ASAS J082243+1927.0和ZZ PsA开展测光与光谱结合的研究，旨在推导自洽的轨道和物理参数，评估它们的演化状态，检验是否已演化至终端不稳定阶段。分析高分辨率VLT/UVES光谱以获取视向速度值、光谱质量比和金属丰度，将结果与蒙特卡洛框架下的多波段光变曲线建模结合，确定系统几何结构和绝对参数。通过O-C分析研究轨道周期变化，利用达尔文不稳定性判据、临界质量比估计值、填充因子和轨道周期变化评估系统演化状态。推导得到AL Lep、ASAS J082243+1927.0和ZZ PsA的质量比q分别为0.1332、0.1041和0.0789，对应的主星质量M1分别为1.656±0.081太阳质量、1.275±0.078太阳质量和1.795±0.111太阳质量。它们的组分位置与单星零龄主序（ZAMS）和终端主序（TAMS）参考曲线存在显著偏差，表明存在强烈的双星相互作用及公共包层的能量再分配。AL Lep和ASAS J082243+1927.0的自旋-轨道角动量比低于标准达尔文不稳定性阈值，而ZZ PsA接近不稳定区域，在推导的不确定度范围内可能对应不稳定构型。
英文摘要
Contact binaries (CBs) are key systems for investigating the late evolutionary stages that may lead to stellar coalescence. Systems with an extremely low mass ratio and high fill-out factor are of particular interest as potential merger candidates and possible progenitors of luminous red novae. A combined photometric and spectroscopic study of the CB systems AL Lep, ASAS J082243+1927.0, and ZZ PsA is presented. The aim is to derive self-consistent orbital and physical parameters, assess their evolutionary state, and examine whether they have reached the terminal and unstable phase of their evolution. High-resolution VLT/UVES spectra were analysed to derive radial velocity values, spectroscopic mass ratio, and metallicity. The results were combined with multi-band light-curve modelling within a Monte Carlo framework to determine the system geometries and absolute parameters. Orbital period variations were investigated through O-C analysis, while the evolutionary status of the systems was assessed using the Darwin instability criterion, critical mass ratio estimates, fill-out factor, and orbital period variation. Mass ratio values of q = 0.1332, 0.1041, and 0.0789 were derived for AL Lep, ASAS J082243+1927.0, and ZZ PsA, respectively. The corresponding primary mass values are M1 = 1.656 +/- 0.081 Msun, 1.275 +/- 0.078 Msun, and 1.795 +/- 0.111 Msun. The locations of their components show significant deviations from single-star ZAMS and TAMS reference curves, indicating strong binary interaction and energy redistribution through the common envelope. The spin-to-orbital angular momentum ratio for AL Lep and ASAS J082243+1927.0 remains below the standard Darwin instability threshold, while ZZ PsA lies close to the instability regime and may be consistent with an unstable configuration within the derived uncertainties.
