We present the results of numerical simulations of continuum-driven winds of stars that exceed the Eddington limit and compare these against predictions from earlier analytical solutions. Our models are based on the assumption that the stellar atmosphere consists of clumped matter, where the individual clumps have a much larger optical thickness than the matter between the clumps. This `porosity' of the stellar atmosphere reduces the coupling between radiation and matter, since photons tend to escape through the more tenuous gas between the clumps. This allows a star that formally exceeds the Eddington limit to remain stable, yet produce a steady outflow from the region where the clumps become optically thin. We have made a parameter study of wind models for a variety of input conditions in order to explore the properties of continuum-driven winds.
The results show that the numerical simulations reproduce quite closely the analytical scalings. The mass loss rates produced in our models are much larger than can be achieved by line driving. This makes continuum driving a good mechanism to explain the large mass loss and flow speeds of giant outbursts, as observed in eta Carinae and other luminous blue variable (LBV) stars. Continuum driving may also be important in population III stars, since line driving becomes ineffective at low metalicities. We also explore the effect of photon tiring and the limits it places on the wind parameters.
A Limit Relation between Black Hole Mass and H$β$ Width: Testing Super-Eddington Accretion in Active Galactic Nuclei
本文证明了具有超爱丁顿吸积率的活动星系核的H $β$半峰宽度与黑洞质量之间存在极限关系。当黑洞具有超爱丁顿吸积率时，混响映射的经验关系有两种可能的形式。首先，它归结为黑洞质量与由于吸积盘内的光子俘获效应而引起的宽线区域的大小之间的关系。对于Kaspi et al.的经验混响关系，得到了极限关系式为$M_{\rm BH}=(2.9 - 12.6)\times 10^6M_{\odot} (\upsilon_{\rm FWHM}/10^3{\rm km s^{-1}})^{6.67}$，称为爱丁顿极限。其次，如果俘获光子能通过光子泡不稳定性从磁化超爱丁顿吸积盘中逃逸，则爱丁顿极限亮度将被放宽，根据经验混响关系，宽线区的尺寸将被扩大，导致H $β$的宽度相对较窄。我们称之为Begelman极限。利用这个极限关系，对一个由164个活动星系核组成的样本中的超爱丁顿吸积进行了研究。我们发现在Eddington极限线和Begelman极限线之间存在着一些小天体，它们可能是光子捕获和光子泡不稳定性混合结构中的超Eddington吸积体的候选者。对于活动星系核中具有超爱丁顿吸积率的最大质量黑洞，H $β$的最大宽度在$(3.0 - 3.8)\times 10^3$ km s $^{-1}$的范围内.我们认为，这种极限关系更可靠和方便的测试是否源是超爱丁顿和有用的探测超爱丁顿吸积过程的结构。
