发表机构
Astronomical Institute of the Czech Academy of Sciences; Institute of Physics of the Czech Academy of Sciences; Shamakhy Astrophysical Observatory（捷克科学院天文研究所; 捷克科学院物理研究所; 沙马基天体物理观测台）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究分析两颗Be星PY Gem和HD253659的星云与变异性，发现二者测光行为迥异，且星云起源与Be现象物理相关，而非演化恒星。
AI 中文摘要
大质量热星周围存在星云通常表明该天体要么处于演化晚期阶段，要么是密近双星相互作用的稀有产物。本文聚焦于两颗Be星——PY Gem和HD253659，其星云由广域红外巡天探测器（Wide-field Infrared Survey Explorer）探测到。我们通过拟合光谱能量分布估算了它们的基本物理参数，并研究了其变异性。我们将来自多个地面巡天望远镜和凌日系外行星巡天卫星（TESS）的档案测光数据与我们自己的专用多色测光和光谱监测数据相结合，得出结论：尽管两颗恒星的性质相似，但它们的测光变异性却截然不同。对于HD253659，我们探测到了持续的喷发变异性以及发生在2016年至2022年间的一次重大爆发，同时在TESS数据中观测到大量闪烁事件。HD253659在颜色-星等图中还表现出环状行为，这与近极轴视角下星周盘的形成和消散阶段一致。相比之下，在过去约20年中，PY Gem已失去其喷发变异性，仅表现出小幅度的p模式和g模式脉动，使PY Gem被归类为β Cephei混合脉动星。一个非相干的低频信号被识别为Štefl频率，该频率似乎得到发射线轮廓周期性变化的支持。对这些恒星的详细分析表明，两个天体均与演化后的恒星不一致，其星云的起源更可能与Be现象物理学相关。
英文摘要
The presence of a nebula around massive hot stars often works as an indicator that the object is either in an advanced evolutionary stage or a rare product of close binary interaction. Here, we focus on two Be stars - PY Gem and HD253659 - whose nebulae were detected with the Wide-field Infrared Survey Explorer. We estimated their basic physical parameters from modelling the spectral energy distribution and examined their variability. We combined archival photometric data from several ground-based survey telescopes and from the Transiting Exoplanet Survey Satellite (TESS) with our own data from dedicated multi-colour photometric and spectroscopic monitoring, and concluded that, despite having similar stellar properties, the photometric variability of the two objects is strikingly different. For HD253659 we detected continuous eruptive variability and a major outburst that took place between 2016 and 2022 along with numerous flicker events seen in the TESS data. HD253659 also exhibits loop-like behaviour in the colour-magnitude diagram, consistent with build-up and dissipation phases of a circumstellar disk seen close to pole-on. In contrast, during the past ~20 years PY Gem has lost its eruptive variability and shows only small-amplitude p and g-mode pulsations classifying PY Gem as βCephei hybrid pulsator. An incoherent low-frequency signal is identified as a Štefl frequency, which seems to be supported by the cyclic variation of the emission-line profiles. Detailed analysis of these stars indicates that both objects are inconsistent with evolved massive stars, and that the origin of their nebulae is more likely linked to the physics of the Be phenomenon.
Comments19 pages, 16 figures, accepted for publication to MNRAS
