Theoretical pulsation of metallic-line stars
Theoretical pulsation of metallic-line stars
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DOI：
10.1086/157245
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发表时间：
1979-08
期刊：
影响因子：
--
通讯作者：
A. N. Cox;D. S. King;S. Hodson
中科院分区：
文献类型：
--
作者：
A. N. Cox;D. S. King;S. Hodson
本文研究了低氦δ Scuti变星模型（1.0- 2.5Msun）的线性理论径向脉动稳定性，以观察金属性和脉动是否能同时发生。金属化，这发生在缓慢旋转的恒星后，重力沉降的He和损失的He II对流区和它的深度混合为Y<或约。=0.1，则可以与演化时间尺度相比快速地建立。由于残留的氦和增强的氢，在驾驶时仍然会发生脉动。在约化氦没有给出连接区的情况下，脉动不稳定带的蓝色和边缘在本文中被估计，约为正常氦丰度的一半宽。然而，在表面驱动区中的零氦产生的蓝边是如此的红，以至于可能根本不存在不稳定带。根据外区对流的重要性从理论上预测的红边与观测结果非常一致。冷，低氦和金属线的恒星，然后预测脉动在200- 500 K宽的带，是最宽的5 Lsun和15 Lsun之间的主序星光度。这条带合理地包括观察到的脉动三角洲德尔和温和的上午星，但更多的是可能存在冲突。由于蓝边的变化电离区氦含量发生在整个不稳定带，蓝色的第一和更高的泛音脉动也预测无处不在，从小于7000 K到超过8000 K，红色的可能显示金属。«少
The linear-theory radial-pulsation stability of low-helium delta Scuti variable models (1.0--2.5 Msun) has been investigated to see if metallicism and pulsation can occur simultaneously. Metallicism, which occurs in slowly rotating stars after the gravitational settling of He and the loss of the He II convection zone and its deep mixing for Y< or approx. =0.1, can then be established rapidly compared with the evolution time scale. Pulsation can still occur with driving due to the residual helium and the enhanced hydrogen. With the reduced helium giving no connection zone, the pulsation instability strip, whose blue and edges are estimated in this paoer, is about half as wide as with a normal helium abundance. Zero helium in the surface driving regions, however, produces blue edges so red that probably no instability strip exists at all. The red edge, predicted theoretically on the basis of the importance of convection in the outer zone, agrees well with the observational one. Cool, low-helium and metallic-line stars are then predicted to pulsate in a 200--500 K wide strip that is widest between the main-sequence luminosity of 5 Lsun and 15 Lsun. This strip reasonably includes the observed pulsating delta Del and mild Am stars, butmore » there may be conflicts. Since blue edges for varying ionization-zone helium content occur across the entire instability strip, bluer first and higher overtone pulsations are also predicted everywhere from less than 7000 K to over 8000 K, the redder ones probably showing metallicism.« less