3D hydrodynamics simulations of internal gravity waves in red giant branch stars
3D hydrodynamics simulations of internal gravity waves in red giant branch stars
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DOI：
10.1093/mnras/stad1115
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发表时间：
2023-04-21
影响因子：
4.8
通讯作者：
Thompson, William R.
中科院分区：
文献类型：
--
作者：
Blouin, Simon;Mao, Huaqing;Thompson, William R.
本文首次对红巨星分支（RGB）上低质量恒星辐射内部引力波（IGW）的激发和传播进行了三维流体力学模拟。我们使用PPMSTAR显式气体动力学程序模拟了一个1。两米？上RGB星星。我们对不同的网格分辨率（768（3），1536（3）和2880（3）），一系列的驱动光度和两个不同的分层（对应于凹凸光度和RGB的尖端）进行模拟。我们的RGB尖端模拟可以直接在标称亮度下进行，避免了外推到较低亮度的需要。一个丰富的，连续的光谱IGWs观察到，在高波数包含了显着的总功率。通过跟踪稳定层中被动染料的时间演化，我们发现模拟中的IGW混合比基于剪切混合的简单分析处方预测的要弱，并且不足以解释缺少的RGB额外混合。然而，我们可能低估了IGW混合的效率，因为我们的模拟包括对流包络的有限部分。与我们的基准设置相比，将其径向范围扩大四倍，将对流速度提高了2倍，将IGW速度提高了4倍。我们还报告了类似于0的形成。图2 H-P穿透区和IGW是由进入稳定层的羽流激发的证据。
We present the first 3D hydrodynamics simulations of the excitation and propagation of internal gravity waves (IGWs) in the radiative interiors of low-mass stars on the red giant branch (RGB). We use the PPMSTAR explicit gas dynamics code to simulate a portion of the conv ectiv e env elope and all the radiative zone down to the hydrogen-burning shell of a 1 . 2 M-? upper RGB star. We perform simulations for different grid resolutions (768 (3) , 1536 (3) , and 2880 (3) ), a range of driving luminosities, and two different stratifications (corresponding to the bump luminosity and the tip of the RGB). Our RGB tip simulations can be directly performed at the nominal luminosity, circumventing the need for extrapolations to lower luminosities. A rich, continuous spectrum of IGWs is observed, with a significant amount of total power contained at high wavenumbers. By following the time evolution of a passive dye in the stable layers, we find that IGW mixing in our simulations is weaker than predicted by a simple analytical prescription based on shear mixing and not efficient enough to explain the missing RGB extra mixing. Ho we ver, we may be underestimating the efficiency of IGW mixing given that our simulations include a limited portion of the convective envelope. Quadrupling its radial extent compared to our fiducial set-up increases conv ectiv e v elocities by up to a factor 2 and IGW velocities by up to a factor 4. We also report the formation of a similar to 0 . 2 H-P penetration zone and evidence that IGWs are excited by plumes that o v ershoot into the stable layers.