We present a comprehensive characterization of the evolved thermally pulsing asymptotic giant branch (TP-AGB) star R Hydrae (R Hya), building on the techniques applied in Stellar Evolution in Real Time I (Molnár et al.) to T Ursae Minoris. We compute over 3000 theoretical TP-AGB pulse spectra using MESA and the corresponding oscillation spectra with GYRE. We combine these with classical observational constraints and nearly 400 years of measurements of R Hya’s period evolution to fit R Hya’s evolutionary and asteroseismic features. Two hypotheses for the mode driving R Hya’s period are considered. Solutions that identify this as the fundamental mode (FM) as well as the first overtone are consistent with observations. Using a variety of statistical tests, we find that R Hya is most likely driven by the FM and currently occupies the “power-down” phase of an intermediate pulse (TP ∼ 9–16). We predict that its pulsation period will continue to shorten for millennia. Supported by calculations from the Monash stellar evolution code, we find that R Hya has most likely undergone third dredge-up in its most recent pulse. The MESA + GYRE model grid used in this analysis includes exact solutions to the linear, adiabatic equations of stellar oscillation for the first 10 radial-order pressure modes for every time step in every evolutionary track. The grid is fully open source and packaged with a data visualization application. This is the first publicly available grid of TP-AGB models with seismology produced with MESA.

中文翻译：

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实时恒星演化。二. R Hydrae 和使用 MESA 计算的超过 3000 个地震 TP-AGB 模型的开源网格


我们基于《恒星实时演化 I》（Molnár 等人）和 T Ursae Minoris 中应用的技术，对演化的热脉冲渐近巨星分支 (TP-AGB) 恒星 R Hydrae (R Hya) 进行了全面的表征。我们使用以下方法计算了 3000 多个理论 TP-AGB 脉冲光谱台面和相应的振荡谱环流。我们将这些与经典观测约束和近 400 年 R Hya 周期演化的测量结果结合起来，以适应 R Hya 的演化和星震特征。考虑了驱动 R Hya 周期的模式的两个假设。将其识别为基本模式 (FM) 以及第一泛音的解决方案与观察结果一致。通过各种统计测试，我们发现 R Hya 最有可能由 FM 驱动，目前占据中间脉冲的“断电”阶段 (TP ∼ 9-16)。我们预测它的脉动周期将持续缩短数千年。在莫纳什恒星演化代码计算的支持下，我们发现 R Hya 很可能在最近的脉冲中经历了第三次挖掘。这台面+环流该分析中使用的模型网格包括每个演化轨迹中每个时间步的前 10 个径向阶压力模式的恒星振荡线性绝热方程的精确解。该网格是完全开源的，并与数据可视化应用程序打包在一起。这是第一个公开的 TP-AGB 模型网格，其地震学是由台面。