后AGB双星中的喷流形成：将冷磁流体动力学盘风模型与观测进行对比
Jet formation in post-AGB binaries: Confronting cold magnetohydrodynamic disc wind wind models with observations
AI总结：
本文用冷自相似MHD盘风模型拟合五个后AGB双星的喷流观测，约束吸积盘参数，发现可解释多数Balmer alpha特征但仍有系统差异。
摘要：
目的：我们考虑采用冷的自相似磁流体动力学（MHD）盘风解，以描述由后AGB双星中伴星周吸积盘发射的喷流。所得预测与五个不同后AGB双星的观测进行匹配。这既检验了MHD盘风范式的物理有效性，也揭示了吸积盘的性质。结果：模型很好地再现了时间序列的许多性质，但仍存在系统性不匹配，例如高估的旋转。四个目标意味着吸积盘延伸至接近次星的恒星表面，而一个目标拟合得到约20个恒星半径的不切实际的大内半径。一些拟合意味着盘内温度超过10 000 K，似乎与此前H波段干涉测量的观测估计相矛盾。然而，本文表明该估计存在偏差。拟合得到的质量吸积率范围约为每年10^-6至10^-3太阳质量。相对于年轻恒星天体（YSOs）发射的喷流，所有目标都更倾向于具有更高抛射效率、更低磁化强度和更厚盘的风。结论：我们的模型表明，当前的冷MHD盘风解可以解释在后AGB双星中观测到的许多与喷流相关的Balmer alpha特征，但系统性差异仍然存在。这包括但不限于高估的旋转以及低估的后AGB环双星盘寿命。考虑更厚的盘并纳入来自后AGB主星的辐照，从而产生温暖的磁热风发射，或许可以缓解这些问题。
英文摘要：
Aims: We consider cold self-similar magnetohydrodynamic (MHD) disc wind solutions to describe jets that are launched from the circumcompanion accretion discs in post-AGB binaries. Resulting predictions are matched to observations for five different post-AGB binaries. This both tests the physical validity of the MHD disc wind paradigm and reveals the accretion disc properties. Results: Many of the time-series' properties are reproduced well by the models, though systematic mismatches, such as overestimated rotation, remain. Four targets imply accretion discs that reach close to the secondary's stellar surface, while one is fitted with an unrealistically large inner radius of about 20 stellar radii. Some fits imply inner disc temperatures over 10 000 K, seemingly discrepant with a previous observational estimate from H band interferometry. This estimate is, however, shown to be biased. Fitted mass-accretion rates range from about 10^-6 to 10^-3 solar masses per year. Relative to the jets launched from young stellar objects (YSOs), all targets prefer winds with higher ejection efficiencies, lower magnetizations and thicker discs. Conclusions: Our models show that current cold MHD disc wind solutions can explain many of the jet-related Balmer alpha features seen in post-AGB binaries, though systematic discrepancies remain. This includes, but is not limited to, overestimated rotation and underestimated post-AGB circumbinary disc lifetimes. The consideration of thicker discs and the inclusion of irradiation from the post-AGB primary, leading to warm magnetothermal wind launching, might alleviate these.
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