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arXiv 1102.0386astro-ph.SRastro-ph.GA
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大质量恒星的射电观测

Radio observations of massive stars

Ronny Blomme

摘要:

在大质量恒星演化的几乎所有阶段都有可探测到的射电辐射。我将集中讨论早期型恒星的热辐射和非热连续辐射。热射电辐射是由于电离恒星风物质中的自由-自由相互作用。早期的想法是,这将导致一个简单而直接的方法来测量质量损失率,但由于恒星风中的聚集现象而受阻。多波长观测提供了重要的限制,这种结块,但不允许其完全确定。非热射电辐射与二进制有关。这一结论在沃尔夫-拉叶星上已经存在了一段时间,近年来,人们已经清楚地发现它也适用于O型星。在双星系统中,两个恒星风发生碰撞,在激波周围,一小部分电子被加速到相对论速度。这些电子在磁场中螺旋运动时会发出同步辐射,我们探测到的是非热射电辐射。许多影响非热射电通量的参数使得这些系统的建模特别具有挑战性,但他们的研究将为大质量恒星提供有趣的新见解。

英文摘要:

Detectable radio emission occurs during almost all phases of massive star evolution. I will concentrate on the thermal and non-thermal continuum emission from early-type stars. The thermal radio emission is due to free-free interactions in the ionized stellar wind material. Early ideas that this would lead to an easy and straightforward way of measuring the mass-loss rates were thwarted by the presence of clumping in the stellar wind. Multi-wavelength observations provide important constraints on this clumping, but do not allow its full determination. Non-thermal radio emission is associated with binarity. This conclusion was already known for some time for Wolf-Rayet stars and in recent years it has become clear that it is also true for O-type stars. In a massive-star binary, the two stellar winds collide and around the shocks a fraction of the electrons are accelerated to relativistic speeds. Spiralling in the magnetic field these electrons emit synchrotron radiation, which we detect as non-thermal radio emission. The many parameters that influence the resulting non-thermal radio fluxes make the modelling of these systems particularly challenging, but their study will provide interesting new insight into massive stars.

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