A Lagrangian construction of rotating star models
A Lagrangian construction of rotating star models
复制标题
旋转星模型的拉格朗日构造
DOI：
10.1093/mnras/stad647
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发表时间：
2023
影响因子：
4.8
通讯作者：
Shoichi Yamada
中科院分区：
文献类型：
--
作者：
Misa Ogata;Hirotada Okawa;Kotaro Fujisawa;Nobutoshi Yasutake;Yu Yamamoto;Shoichi Yamada
提出了一种新的二维旋转恒星轴对称平衡结构的数值计算公式。为了将其应用到旋转恒星的长期演化中，我们将其建立在拉格朗日描述的基础上，即通过求解力平衡方程来求出具有质量、比熵和角动量的流体元的空间位置。用W4法求解由基本方程有限微分得到的非线性方程组，这是我们自己设计的一种新的多维寻根方案。为了避免拉格朗日坐标的畸变，我们对其进行了扩充。在这一系列论文的第一篇中，我们将首先对这些方法进行详细描述。然后，我们给出了一些测试计算的结果，其中包括快速旋转正压和斜压平衡状态的构建。我们用一些诊断量定量地衡量它们的准确性，并通过与欧拉代码获得的对应量进行比较。为了演示，我们将代码应用于旋转白矮星的玩具模型冷却计算。
We present a new formulation for numerically obtaining axisymmetric equilibrium structures of rotating stars in two spatial dimensions. With a view to apply it to the secular evolution of rotating stars, we base it on the Lagrangian description, i.e. we solve the force-balance equations to find the spatial positions of fluid elements endowed individually with a mass, specific entropy and angular momentum. The system of non-linear equations obtained by finite-differencing the basic equations is solved with the W4 method, which is a new multidimensional root-finding scheme of our own devising. We augment it with a remapping scheme to avoid distortions of the Lagrangian coordinates. In this first one of a series of papers, we will give a detailed description of these methods initially. We then present the results of some test calculations, which include the construction of both rapidly rotating barotropic and baroclinic equilibrium states. We gauge their accuracies quantitatively with some diagnostic quantities as well as via comparisons with the counterparts obtained with an Eulerian code. For a demonstrative purpose, we apply the code to a toy-model cooling calculation of a rotating white dwarf.