arXiv 1209.44962012-09astro-ph.SR

演化大质量恒星周围星周壳层的多维模型

Multi-dimensional models of circumstellar shells around evolved massive stars

Allard Jan van Marle, Rony Keppens

备注：: Accepted for publication in A&A. All figures in low resolution. v2: language corrections and addition of DOI number
DOI：: 10.1051/0004-6361/201218957

摘要：

大质量恒星通过其恒星风的力量塑造其周围的介质，恒星风与星周介质碰撞。由于这些恒星风的特征在恒星演化过程中会发生变化，星周物质成为恒星演化的反映，可以用来确定祖星的特征。特别是，当一个快风相位跟随着一个慢风相位时，快风会将它的前身扫到一个壳层中，这个壳层被观测为一个星周星云。我们做2-D和3-D的数值模拟快速恒星风扫了他们的缓慢的前辈，调查这些壳的数值模型是否必须是3-D的，或者2-D模型是否足以正确地再现壳。我们专注于这些情况下，快速沃尔夫-拉叶（WR）星风席卷了其前身，无论是一个红色的超巨星或发光的蓝色变量发出的较慢的风。当快速WR风膨胀时，它会产生一个由被冲击的WR风的高压驱动的向外膨胀的被扫起的物质的致密外壳。这些壳层受到各种各样的流体动力学辐射不稳定性的影响。如果WR风扩展成明亮的蓝色变相风，不稳定性将倾向于形成一个相当小的尺度，规则的连续晶格，细丝连接多节的特征。如果WR风扫过红超巨星风，不稳定性将形成更大的相互连接的结构，而规则性较低。我们的研究结果表明，3-D模型，当翻译到观察到的形态，给出了现实的结果，可以直接比较观察。星云的三维结构将有助于区分不同的祖先场景。

英文摘要：

Massive stars shape their surrounding medium through the force of their stellar winds, which collide with the circumstellar medium. Because the characteristics of these stellar winds vary over the course of the evolution of the star, the circumstellar matter becomes a reflection of the stellar evolution and can be used to determine the characteristics of the progenitor star. In particular, whenever a fast wind phase follows a slow wind phase, the fast wind sweeps up its predecessor in a shell, which is observed as a circumstellar nebula. We make 2-D and 3-D numerical simulations of fast stellar winds sweeping up their slow predecessors to investigate whether numerical models of these shells have to be 3-D, or whether 2-D models are sufficient to reproduce the shells correctly. We focus on those situations where a fast Wolf-Rayet (WR) star wind sweeps up the slower wind emitted by its predecessor, being either a red supergiant or a luminous blue variable. As the fast WR wind expands, it creates a dense shell of swept up material that expands outward, driven by the high pressure of the shocked WR wind. These shells are subject to a fair variety of hydrodynamic-radiative instabilities. If the WR wind is expanding into the wind of a luminous blue variable phase, the instabilities will tend to form a fairly small-scale, regular filamentary lattice with thin filaments connecting knotty features. If the WR wind is sweeping up a red supergiant wind, the instabilities will form larger interconnected structures with less regularity. Our results show that 3-D models, when translated to observed morphologies, give realistic results that can be compared directly to observations. The 3-D structure of the nebula will help to distinguish different progenitor scenarios.

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