arXiv 0708.41992007-08astro-ph

行星状星云原理与范例：双星、吸积、磁场

Planetary Nebulae Principles & Paradigms: Binaries, Accretion, Magnetic Fields

Eric G. Blackman, Jason T. Nordhaus

备注：: 8 pages, 1 figure; for the proceedings of "Asymmetric Planetary Nebuale IV," R. L. M. Corradi, A. Manchado, N. Soker eds

摘要：

观测表明，许多（如果不是全部的话）后AGB系统通过非球面流出阶段演化。这样的外流需要足够的发动机旋转能量，而双星可以提供。通过共同的包层演化，双星可以直接喷射赤道流出或产生极向流出从磁化吸积盘周围的主要或次要。我们讨论如何吸积驱动的磁流体外流模型都作出类似的预测的外流功率和速度，我们区分发射与传播制度，这样的外流。我们认为，在行星状星云（PNe）中观察到的高速双极流出和在前行星状星云（PNe）中观察到的低速但高功率的双极流出在运动学上与耗尽包层内的白矮星（WD）上的依赖于时间的吸积是一致的。由于WD主核总是存在于所有后AGB系统中，因此在此核上的吸积可能是常见的。之前的工作重点是亚恒星伴星的核心吸积，但低质量恒星伴星可能更重要，需要进一步的工作。

英文摘要：

Observations suggest that many, if not all, post AGB systems evolve through an aspherical outflow phase. Such outflows require a sufficient engine rotational energy which binaries can provide. Via common envelope evolution, binaries can directly eject equatorial outflows or produce poloidal outflows from magnetized accretion disks around the primary or secondary. We discuss how accretion driven magnetohydrodynamic outflow models all make similar predictions for the outflow power and speed and we distinguish between the launch vs. propagation regimes of such outflows. We suggest that the high velocity bipolar outflows observed in planetary nebulae (PNe) and the lower velocity but higher power bipolar outflows observed in pre-PNe (pPNe) are kinematically consistent with time dependent accretion onto a white dwarf (WD) within a depleting envelope. Since the WD primary core is always present in all post-AGB systems, accretion onto this core is potentially common. Previous work has focused on core accretion from sub-stellar companions, but low mass stellar companions may be more important, and further work is needed.

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