Radiation Hydrodynamics of Winds from Hot Stars

早在本世纪初，人们就提出了热恒星辐射压力对恒星风的驱动作用，自那以后，人们发现它可以很好地解释各种天文物体的质量损失，从非常热的(O型)恒星，到活跃的星系核，再到类星体。在过去NSF支持的工作中，首席调查员(PI)已经证明了早期辐射驱动风概念的根本缺陷。例如，现在很明显，光子在密集风中的散射抑制了自感不稳定的增长，因此风只会产生轻微的不均匀。然而，在光学和紫外谱线上都观察到了这种不稳定性，并被认为表明存在以不同速度移动的碰撞风。这些碰撞产生的冲击可能是具有辐射驱动风的物体中X射线的主要来源。有了这个为期三年的奖项，PI和一名博士后研究员将用更现实的大气模型开发数值模拟，并将早期的分析解决方案扩展到二维甚至三维。这项工作将评估湍流不稳定性在通过风流的不均匀演变中的作用。预计这项工作最终将广泛应用于除O星以外的河外天体。

The driving of stellar winds from the radiation pressure of hot stars was suggested early in the century, and has since been found to provide a good explanation of mass loss in a wide variety of astronomical objects, ranging from very hot ("O-type") stars, to active galactic nuclei, to quasars. In past NSF supported work the Principal Investigator (PI) has demonstrated fundamental flaws in earlier concepts of radiatively driven winds. For example, it is now clear that scattering of photons in dense winds inhibits the growth of self-induced instabilities so that the winds only develop mild inhomogeneities. However, such instabilities have been observed in both optical and ultraviolet spectral lines and are thought to indicate the presence of colliding winds moving at different speeds. The shocks generated by these collisions may be the primary source of x-rays in objects with radiatively driven winds. With this three-year award the PI and a postdoctoral fellow will develop numerical simulations with more realistic atmospheric models and to extend earlier analytical solutions to two and even three dimensions. This work will assess the role of turbulent instabilities in the evolution of inhomogeneities through the wind flow. It is expected that this work will ultimately have a wide application to extragalactic objects in addition to O stars.