PPN作为爆炸：子弹与喷气机和星云成形
PPN as Explosions: Bullets vs Jets and Nebular Shaping
摘要：
许多原行星状星云（PPN）看起来像是狭窄的准直结构，有时会显示出多个大致对齐的叶瓣。此外，许多PPN流已被证明具有短的加速时间。在本文中，我们探讨是否射流或“子弹”（一个巨大的团块）模型适合单独的准直叶充分通过比较模拟辐射冷却（稳定）的喷气机和子弹的意见。我们发现，在某种程度上，团簇模型比喷流更受青睐，因为（1）它导致更大的流出准直（2）它更好地解释了在PPN CRL 618中观察到的环状结构，（3）它更成功地再现了在一些PPN中观察到的运动学的哈勃流特征。此外，子弹自然地解释了观察到的多极流，因为驱动外流所需的可能的MHD发射机制使得多个不对准的射流不太可能。因此，我们认为，PPN外流可能是由爆炸MHD发射机制，如在超新星（SNe）和伽马射线暴（GRB）的背景下讨论的。
英文摘要：
Many proto-planetary nebulae (PPN) appear as narrow collimated structures sometimes showing multiple, roughly aligned lobes. In addition, many PPN flows have been shown to have short acceleration times. In this paper we explore whether jet or ``bullet'' (a massive clump) models fit the observations of individual collimated lobes adequately by comparing simulations of both radiatively cooled (stable) jets and bullets. We find that the clump model is somewhat favored over jets because (1) it leads to greater collimation of outflows (2) it accounts better and more naturally for ring-like structures observed in the PPN CRL 618, and (3) it is more successful in reproducing the Hubble-flow character of observed kinematics in some PPN. In addition, bullets naturally account for observed multipolar flows, since the likely MHD launch mechanisms required to drive outflows make multiple non-aligned jets unlikely. Thus we argue that PPN outflows may be driven by explosive MHD launch mechanisms such as those discussed in the context of supernovae (SNe) and gamma-ray bursts(GRB).
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