Sub-surface convection zones in hot massive stars and their observable consequences
Sub-surface convection zones in hot massive stars and their observable consequences
复制标题
DOI：
10.1051/0004-6361/200911643
复制
发表时间：
2009-03
影响因子：
6.5
通讯作者：
M. Cantiello;N. Langer;N. Langer;I. Brott;A. D. Koter;A. D. Koter;S. Shore;J. Vink;A. Voegler;D. Lennon;S.-C. Yoon
中科院分区：
文献类型：
--
作者：
M. Cantiello;N. Langer;N. Langer;I. Brott;A. D. Koter;A. D. Koter;S. Shore;J. Vink;A. Voegler;D. Lennon;S.-C. Yoon
上下文。我们研究了热大质量恒星外包层中的对流区，这些对流区是由铁和氦电离相关的不透明峰引起的。目标。我们确定了这些对流区的出现和性质是恒星参数的函数。然后，我们将我们的结果与对OB恒星的观测结果进行对比。方法：研究方法。恒星演化代码被用来计算不同金属含量的大质量恒星模型的网格。在这些模型中，混合长度理论被用来描述包络对流区。结果。我们发现，表面重力越低，光度越高，初始金属丰度越高，铁对流区(FeCZ)越突出。在103.2 L⊙、103.9 L⊙和104.2 L⊙以下，银河系、大片积云和小片积体的亮度都不存在。我们将FeCZ的强度映射到三种金属元素的Hertzsprung-Russell图上，并将其与O星中发生的观测现象进行比较：微湍流、非径向脉动、风团和线型变化。结论。用经验微湍流速度证实了FeCZ作为恒星参数的函数的三种趋势，证明了O型和B型恒星的光球亚光球对流运动和光球小尺度随机速度之间存在物理联系。我们进一步认为，OB星风的内部聚集可能是由相同的机制引起的，并且根据紫外线吸收线中离散的吸收成分的诊断，FeCZ产生的磁场可能出现在OB恒星的表面。
Context. We study the convection zones in the outer envelope of hot massive stars which are caused by opacity peaks associated with iron and helium ionization. Aims. We determine the occurrence and properties of these convection zones as function of the stellar parameters. We then confront our results with observations of OB stars. Methods. A stellar evolution code is used to compute a grid of massive star models at different metallicities. In these models, the mixing length theory is used to characterize the envelope convection zones. Results. We find the iron convection zone (FeCZ) to be more prominent fo r lower surface gravity, higher luminosity and higher initi al metallicity. It is absent for luminosities below about 10 3.2 L⊙, 10 3.9 L⊙, and 10 4.2 L⊙ for the Galaxy, LMC and SMC, respectively. We map the strength of the FeCZ on the Hertzsprung-Russell diagram for three metallicities, and compare this with the occurrence of observational phenomena in O stars: microturbulence, non-radial pulsations, wind clumping, and line profile variabil ity. Conclusions. The confirmation of all three trends for the FeCZ as function o f stellar parameters by empirical microturbulent velociti es argues for a physical connection between sub-photospheric convective motions and small scale stochastic velocities i n the photosphere of O- and B-type stars. We further suggest that clumping in the inner parts of the winds of OB stars could be caused by the same mechanism, and that magnetic fields produced in the FeCZ coul d appear at the surface of OB stars as diagnosed by discrete absorption components in ultraviolet absorption lines.