DOUBLE BOW SHOCKS AROUND YOUNG, RUNAWAY RED SUPERGIANTS: APPLICATION TO BETELGEUSE
DOUBLE BOW SHOCKS AROUND YOUNG, RUNAWAY RED SUPERGIANTS: APPLICATION TO BETELGEUSE
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年轻、失控的红超巨星周围的双弓电击：对参宿四的应用
DOI：
10.1088/2041-8205/751/1/l10
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
D. Meyer
中科院分区：
文献类型：
--
作者：
J. Mackey;S. Mohamed;H. Neilson;N. Langer;D. Meyer
大质量恒星中有相当一部分以超音速方式穿过星际介质（ISM），这要么是由于双星系统的破坏，要么是由于它们的母星星团的抛射。它们的风与ISM的相互作用产生了弓形激波。在演化的后期，这些恒星可能会在赫兹-罗素图上经历从红色到蓝色的快速转变，反之亦然，伴随着恒星风和弓形激波的快速变化。最近，在恒定风的假设下，对附近逃逸的红超巨星参宿四（RSG）产生的弓形激波进行了三维模拟，结果表明弓形激波非常年轻（<30，000年），因此参宿四可能只是最近才成为RSG。为了测试这种可能性，我们计算了恒星演化模型的单星相匹配的观测性能的参宿四在RSG阶段。由此产生的恒星风的演变被纳入到二维流体动力学模拟中，我们模拟一个失控的蓝超巨星（BSG），因为它经历了过渡到RSG接近其生命的结束。我们发现，崩溃的BSG风气泡诱导弓激波形状的内壳周围的RSG风，类似于参宿四的弓激波，并具有类似的质量。围绕着它的是由现在已经不存在的BSG风与ISM相互作用产生的更大规模的后退弓形激波。我们认为，这种外壳可以解释位于参宿四弓形激波前面的条状特征（至少在投影中）。
A significant fraction of massive stars are moving supersonically through the interstellar medium (ISM), either due to disruption of a binary system or ejection from their parent star cluster. The interaction of their wind with the ISM produces a bow shock. In late evolutionary stages these stars may undergo rapid transitions from red to blue and vice versa on the Hertzsprung–Russell diagram, with accompanying rapid changes to their stellar winds and bow shocks. Recent three-dimensional simulations of the bow shock produced by the nearby runaway red supergiant (RSG) Betelgeuse, under the assumption of a constant wind, indicate that the bow shock is very young (<30, 000 years old), hence Betelgeuse may have only recently become an RSG. To test this possibility, we have calculated stellar evolution models for single stars which match the observed properties of Betelgeuse in the RSG phase. The resulting evolving stellar wind is incorporated into two-dimensional hydrodynamic simulations in which we model a runaway blue supergiant (BSG) as it undergoes the transition to an RSG near the end of its life. We find that the collapsing BSG wind bubble induces a bow shock-shaped inner shell around the RSG wind that resembles Betelgeuse's bow shock, and has a similar mass. Surrounding this is the larger-scale retreating bow shock generated by the now defunct BSG wind's interaction with the ISM. We suggest that this outer shell could explain the bar feature located (at least in projection) just in front of Betelgeuse's bow shock.