A study of convective core overshooting as a function of stellar mass based on two-dimensional hydrodynamical simulations
A study of convective core overshooting as a function of stellar mass based on two-dimensional hydrodynamical simulations
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DOI：
10.1093/mnras/stad009
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发表时间：
2023-03-01
影响因子：
4.8
通讯作者：
Pratt, J.
中科院分区：
文献类型：
--
作者：
Baraffe, I;Clarke, J.;Pratt, J.
我们进行了二维（2D）的核心对流的零年龄主序星覆盖的质量范围从3到20 M圆点的数值模拟。仿真是用完全可压缩的时间隐式代码music进行的。我们研究了过冲的效率，它描述了穿越对流边界的对流流的弹道过程，作为恒星质量和光度的函数。我们还研究了人为增加恒星光度对3 M圆点模型的影响。模拟涵盖数百至数千对流周转时间尺度。应用框架的极端羽流事件以前开发的对流信封，我们得到过冲长度作为恒星质量的函数。我们发现，超调距离（d（ov））与恒星光度（L）和对流核半径（r（conv））成比例。我们推导出一个比例律d（ov）L（1/3）r（conv）（1/2），这是实现在一个一维恒星演化的代码和由此产生的恒星模型进行比较的观察。缩放预测的超调距离，显着增加恒星质量的值，在定性与观测一致。然而，定量地，对于大于或类似于10 M圆点的质量，预测值被低估。我们的二维模拟显示，形成一个几乎绝热层的史瓦西边界的对流核心，在最近的三维对流模拟所展示的。最明亮的模型显示，随着时间的推移，几乎绝热层的大小增长。这种增长似乎放缓的近绝热层的上边缘越来越接近最大过冲长度，并作为模拟时间超过典型的热扩散时间尺度的过冲层。
We perform two-dimensional (2D) numerical simulations of core convection for zero-age main-sequence stars covering a mass range from 3 to 20 M-circle dot. The simulations are performed with the fully compressible time-implicit code music. We study the efficiency of overshooting, which describes the ballistic process of convective flows crossing a convective boundary, as a function of stellar mass and luminosity. We also study the impact of artificially increasing the stellar luminosity for 3 M-circle dot models. The simulations cover hundreds to thousands of convective turnover time-scales. Applying the framework of extreme plume events previously developed for convective envelopes, we derive overshooting lengths as a function of stellar masses. We find that the overshooting distance (d(ov)) scales with the stellar luminosity (L) and the convective core radius (r(conv)). We derive a scaling law d(ov) proportional to L(1/3)r(conv)(1/2), which is implemented in a one-dimensional stellar evolution code and the resulting stellar models are compared to observations. The scaling predicts values for the overshooting distance that significantly increase with stellar mass, in qualitative agreement with observations. Quantitatively, however, the predicted values are underestimated for masses greater than or similar to 10 M-circle dot. Our 2D simulations show the formation of a nearly adiabatic layer just above the Schwarzschild boundary of the convective core, as exhibited in recent three-dimensional simulations of convection. The most luminous models show a growth in size with time of the nearly adiabatic layer. This growth seems to slow down as the upper edge of the nearly adiabatic layer gets closer to the maximum overshooting length and as the simulation time exceeds the typical thermal diffusive time-scale in the overshooting layer.