Establishing a multi-dimensional framework to benchmark Wolf-Rayet-type outflows

大质量恒星短暂而充满活力的生命对整个星系的演化至关重要，无论是在宇宙早期还是现在。由于它们的高亮度，大质量恒星可以电离它们周围的环境，并以所谓的恒星风的形式排出它们的最外层。这种辐射驱动的风影响着邻近的星际物质和宿主恒星自身的进化路径。在生命的尽头，大质量恒星会坍缩成中子星和黑洞等奇异的残留物——统称为致密天体（CO）。这种坍缩是否伴随着超新星爆炸，以及形成哪种类型的遗迹，在很大程度上取决于恒星的最终质量，强调关于先前质量损失的定量知识至关重要。随着最近引力波天文学的出现和越来越多的CO合并探测，了解大质量恒星的影响和进化途径的需求只会进一步增长。这个项目致力于研究大质量恒星进化之谜的一个重要部分：经典的沃尔夫-拉叶（WR）恒星是在强大的风的作用下，在核心坍缩的过程中进化而来的恒星。这一演化阶段的质量损失非常大，通常决定了CO残余物的质量和类型。尽管WR星在现代天体物理学中起着至关重要的作用，但对WR风的发射和加速过程的定性和定量认识仍然很初级，因此在当前的演化和种群综合模型中造成了很大的不确定性。这种不确定性源于这样一个事实，即确定WR特性（例如，风速、密度结构、质量损失和涌现光谱）需要复杂的数值辐射-流体动力学计算。到目前为止，这种计算的数值成本阻碍了一维稳态处理之外的详细模拟。在这个项目中，我们结合了建模技术的两项最新进展，以超越这一限制，并创建了第一个三维网格，WR风外流及其光谱的时间依赖模型。我们项目的基石是对辐射力计算方法的改进，这为水动力规范中WR风的数值处理开辟了新的视角。我们将根据最先进的建模技术实施、测试和测试我们的新方法。然后，我们将创建一个模型网格，覆盖质量、光度、半径和金属丰度的大参数空间。这个网格将使我们能够对WR星的新质量损失处理进行参数化，并创建一个广泛的光谱库，我们将使用它来校准更详细的光谱合成代码。

The short but vibrant life of massive stars is critical for the evolution of whole galaxies, both in the early times of the Universe and now. With their high luminosity, massive stars can ionise their surroundings and expel their outermost layers in the form of a so-called stellar wind. Such radiation-driven winds affect the neighbouring interstellar matter and the evolutionary pathway of the host stars themselves.At the end of their life, massive stars collapse into exotic remnants like neutron stars and black holes - collectively referred to as compact objects (CO). Whether this collapse is accompanied by a supernova explosion and which type of remnant is formed is largely determined by the final mass of the star, stressing that the quantitative knowledge about prior mass loss is crucial. With the recent advent of gravitational wave astronomy and an ever-growing number of CO merger detections, the need to understand massive stars’ influence and evolutionary pathways has only grown further. This project is dedicated to an important piece of the evolutionary puzzle of massive stars: Classical Wolf-Rayet (WR) stars are evolved stars on the way to core-collapse with powerful winds. The mass loss in this evolutionary stage is so large that it usually determines the mass and type of the CO remnant.Despite the critical role of WR stars in modern astrophysics, the qualitative and quantitative insights into the processes participating in the launch and acceleration of WR winds are still rudimentary, thus causing major uncertainties in current evolution and population synthesis models. This uncertainty stems from the fact that the determination of WR properties (e.g., wind velocity, density structure, mass loss, and emergent spectra) requires complicated numerical radiation-hydrodynamics computations. The numerical costs of such calculations have so far prevented detailed simulations beyond one-dimensional steady-state treatments. In this project, we combine two recent advances in modelling techniques to reach beyond this limit and to create the first grid of three-dimensional, time-dependent models of WR wind outflows and their spectra. Our projects’ cornerstone is a refinement of the radiation force computation method, which opens a new perspective for the numerical treatment of WR winds within hydrodynamic codes. We will implement, test, and benchmark our new method against state-of-the-art modelling techniques. We will then create a grid of models covering a large parameter space in masses, luminosities, radii and metallicities. This grid will allow us to parametrise a new mass-loss treatment for WR stars and create an extensive spectral library, which we will use to calibrate a more detailed spectral synthesis code.