标题： 12（DD）天鹰座β仙王座星振荡研究：光变观测、脉动频率分析和模式识别 显示英文标题

标题： Asteroseismology of the Beta Cephei star 12 (DD) Lacertae: photometric observations, pulsational frequency analysis and mode identification

摘要： 我们报告了针对仙王座β型变星12天琴座的多点测光观测活动。在190个夜晚里，使用9台望远镜获得了750小时高质量的微分光电斯特龙根、约翰逊和日内瓦时序测光数据。我们的频率分析结果显示，在亮度曲线中检测到23个正弦信号。其中11个对应于独立的脉动模式，其余的是组合频率。我们发现了一些缓慢的非周期性变化，类似于在几个仙王座β型变星中似乎存在的变化。我们从颜色测光中进行模式识别，明确推导出五个最强模式的球度l值，并对较弱模式的l值提供约束条件。我们发现混合模式的l值范围为0到4。特别是，我们证明了之前怀疑的12天琴座模式内的旋转分裂三重态实际上由不同l值的模式组成；因此，它们的频率分裂必须是偶然的。我们在亮度曲线中检测到的一个周期信号被认为是一个通过2:1共振激发至可见振幅的线性稳定模式。我们还发现在亮度变化中的一个低频信号，其物理性质尚不清楚；它可能是母模式或子模式的共振耦合。剩余的组合频率与简单的亮度曲线畸变一致。12天琴座激发的脉动频率范围可能足够大，以至于无法被标准模型再现。我们怀疑该恒星在脉动驱动区域具有更高的金属丰度，这一假设也能解释为何仙王座β型变星存在于大麦哲伦云中。 显示英文摘要

摘要： We report a multisite photometric campaign for the Beta Cephei star 12 Lacertae. 750 hours of high-quality differential photoelectric Stromgren, Johnson and Geneva time-series photometry were obtained with 9 telescopes during 190 nights. Our frequency analysis results in the detection of 23 sinusoidal signals in the light curves. Eleven of those correspond to independent pulsation modes, and the remainder are combination frequencies. We find some slow aperiodic variability such as that seemingly present in several Beta Cephei stars. We perform mode identification from our colour photometry, derive the spherical degree l for the five strongest modes unambiguously and provide constraints on l for the weaker modes. We find a mixture of modes of 0 <= l <= 4. In particular, we prove that the previously suspected rotationally split triplet within the modes of 12 Lac consists of modes of different l; their equal frequency splitting must thus be accidental. One of the periodic signals we detected in the light curves is argued to be a linearly stable mode excited to visible amplitude by nonlinear mode coupling via a 2:1 resonance. We also find a low-frequency signal in the light variations whose physical nature is unclear; it could be a parent or daughter mode resonantly coupled. The remaining combination frequencies are consistent with simple light-curve distortions. The range of excited pulsation frequencies of 12 Lac may be sufficiently large that it cannot be reproduced by standard models. We suspect that the star has a larger metal abundance in the pulsational driving zone, a hypothesis also capable of explaining the presence of Beta Cephei stars in the LMC.