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arXiv 2012.05823astro-ph.SR
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经典Wolf-Rayet星的动力膨胀风模型

Dynamically inflated wind models of classical Wolf-Rayet stars

L. G. Poniatowski, J. O. Sundqvist, N. D. Kee, S. P. Owocki, P. Marchant, L. Decin, A. de Koter, L. Mahy, H. Sana

备注：
15 pages, 9 figures
发表信息：
A&A 647, A151 (2021)
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摘要：

经典Wolf-Rayet相的剧烈质量损失对大质量恒星的后期演化和最终命运具有重要意义。我们开发了球对称的时间依赖性和稳态流体动力学模型的辐射驱动的风外流和相关的质量损失从经典WR星。模拟的基础上相结合的不透明度通常用于静态恒星结构和演化模型与一个简单的参数化形式的增强线不透明度预期在超音速外流。我们的模拟揭示了高质量损失率开始在深和热的光学厚层T \approx 200 kK左右。由此产生的速度结构是非单调的，可以分为三个阶段：i）初始加速到超音速，ii）停滞甚至减速，iii）快速再加速的外部区域。在收敛的稳态模拟中看到的特征结构与我们的时间相关模型的流出特性吻合得很好。通过直接比较我们的动态模拟相应的流体静力学模型，我们明确表明，需要调用额外的能量传输对流效率低下的地区的恒星结构和演化模型仅仅是一个人工制品的执行流体静力学的外边界。此外，“动态膨胀”的内部区域，我们的模拟提供了一个自然的解释，经常发现预测的流体静力学WR半径和那些从光谱推断之间的不匹配。最后，我们对比我们的模拟与替代最近WR风模型的基础上，共同移动的框架辐射转移计算辐射力。由于CMF传输目前不能处理非单调的速度场，在这里发现的特征减速区域在这样的模拟中通过调用一个特设的非常高的聚集度来避免。

英文摘要：

Vigorous mass loss in the classical Wolf-Rayet (WR) phase is important for the late evolution and final fate of massive stars. We develop spherically symmetric time-dependent and steady-state hydrodynamical models of the radiation-driven wind outflows and associated mass loss from classical WR stars. The simulations are based on combining the opacities typically used in static stellar structure and evolution models with a simple parametrised form for the enhanced line-opacity expected within a supersonic outflow. Our simulations reveal high mass-loss rates initiated in deep and hot optically thick layers around T\approx 200kK. The resulting velocity structure is non-monotonic and can be separated into three phases: i) an initial acceleration to supersonic speeds ii) stagnation and even deceleration, and iii) an outer region of rapid re-acceleration. The characteristic structures seen in converged steady-state simulations agree well with the outflow properties of our time-dependent models. By directly comparing our dynamic simulations to corresponding hydrostatic models, we demonstrate explicitly that the need to invoke extra energy transport in convectively inefficient regions of stellar structure and evolution models is merely an artefact of enforcing a hydrostatic outer boundary. Moreover, the "dynamically inflated" inner regions of our simulations provide a natural explanation for the often-found mismatch between predicted hydrostatic WR radii and those inferred from spectroscopy. Finally, we contrast our simulations with alternative recent WR wind models based on co-moving frame radiative transfer for computing the radiation force. Since CMF transfer currently cannot handle non-monotonic velocity fields, the characteristic deceleration regions found here are avoided in such simulations by invoking an ad-hoc very high degree of clumping.

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