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arXiv 0802.2238astro-ph
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御夫座经典双星的轨道和脉动

Orbits and Pulsations of the Classical ζAurigae Binaries

Joel A. Eaton, Gregory W. Henry, Andrew P. Odell

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Accepted for publication in ApJ
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摘要：

我们已经推导出新的轨道zeta Aur，32 Cyg和31 Cyg与观测从TSU自动光谱望远镜，并使用它们来确定非轨道速度的冷超巨星组件这些系统。我们测量这些偏差的周期，确定径向速度的意外长周期变化，并对这些恒星的旋转设置上限。这些径向速度的变化与径向脉动理论并不明显一致，因为我们知道的质量和大小的组成部分。我们的同步测光检测到非径向脉动驱动的潮汐（椭球变化）在zeta Aur和32 Cyg，在一个水平和相位大致符合简单的理论一阶，虽然他们似乎需要适度大的重力暗化。然而，天鹅座32的K分量必须比预期的大得多，或者有比Aur更大的重力暗化，才能符合它的振幅。然而，在我们的测光中，冷星的正常径向脉动的证据又少得可怜。在zeta Aur和32 Cyg中，H-α显示了B成分加热色球层的一些证据，并且这三颗恒星在它们的风中显示出偶尔在冷超巨星中看到的那种微弱的~ 2--3爆发。我们指出了解释这些恒星的两个基本问题，（1）将表面亮度模拟为重力变暗是否合适，以及（2）大部分非轨道速度结构是否实际上代表了恒星大气中对流的变化。

英文摘要：

We have derived new orbits for zeta Aur, 32 Cyg, and 31 Cyg with observations from the TSU Automatic Spectroscopic Telescope and used them to identify non-orbital velocities of the cool supergiant components of these systems. We measure periods in those deviations, identify unexpected long-period changes in the radial velocities, and place upper limits on the rotation of these stars. These radial-velocity variations are not obviously consistent with radial pulsation theory, given what we know about the masses and sizes of the components. Our concurrent photometry detected the non-radial pulsations driven by tides (ellipsoidal variation) in both zeta Aur and 32 Cyg, at a level and phasing roughly consistent with simple theory to first order, although they seem to require moderately large gravity darkening. However, the K component of 32 Cyg must be considerably bigger than expected, or have larger gravity darkening than zeta Aur, to fit its amplitude. However, again there is precious little evidence for the normal radial pulsation of cool stars in our photometry. H-alpha shows some evidence for chromospheric heating by the B component in both zeta Aur and 32 Cyg, and the three stars show among them a meager ~ 2--3 outbursts in their winds of the sort seen occasionally in cool supergiants. We point out two fundamental questions in the interpretation of these stars, (1) whether it is appropriate to model the surface brightness as gravity darkening and (2) whether much of the non-orbital velocity structure may actually represent changes in the convective flows in the stars' atmospheres.

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