船底座η星的长周期光谱变化：是否如CMFGEN模型所示由消散的掩蔽体引起？
The long-term spectral changes of eta Carinae: are they caused by a dissipating occulter as indicated by CMFGEN models?
AI总结：
本文通过增加轨道周期和原子跃迁的CMFGEN建模，论证船底座η星的光谱长期变化更可能由视线方向消散的星周掩蔽体而非主星质量损失率降低引起，并将大爆发恢复时标缩短至少于一个世纪。
摘要：
船底座η星（η Car）展现出一组独特的P Cygni谱线轮廓，同时具有宽线和窄线成分。在数十年间，其光谱发生了变化——观测到的连续谱流量增加，而FeII和HI发射线的等值宽度减小。该光谱正在向诸如P Cygni本身和HDE 316285这类P Cygni型恒星的光谱演化。这种光谱演化曾被归因于内禀变化，例如主星质量损失率的降低，或随纬度变化的恒星风中的差异演化。然而，内禀恒星风变化与三项观测结果相冲突：长期稳定的热光度；在双星轨道周期上重复的X射线光变曲线；以及来自侏儒星云（Homunculus）的尘埃散射光谱的恒定性。我们扩展了先前显示P Cygni吸收线长期增强的工作，增加了更多轨道周期以克服暂时不稳定性，并考察了更多原子跃迁。对主星星风的CMFGEN建模表明，随时间减小的质量损失率并非对观测结果的最佳解释。然而，在我们视线方向上存在一个“小型”消散吸收体的模型可以同时解释亮度的增加以及发射线和P Cygni吸收轮廓的变化。如果光谱演化是由正在消散的星周介质引起，而非由双星系统的内禀变化引起，那么从大爆发（Great Eruption）中恢复的动力学时标远小于一个世纪，这与先前的建议不同。
英文摘要：
Eta Carinae ($η$\,Car) exhibits a unique set of P Cygni profiles with both broad and narrow components. Over many decades, the spectrum has changed -- there has been an increase in observed continuum fluxes and a decrease in FeII and HI emission line equivalent widths. The spectrum is evolving towards that of a P Cygni star such as P~Cygni itself and HDE~316285. The spectral evolution has been attributed to intrinsic variations such as a decrease in the mass-loss rate of the primary star or differential evolution in a latitudinal-dependent stellar wind. However intrinsic wind changes conflict with three observational results: the steady long-term bolometric luminosity; the repeating X-ray light curve over the binary period; and the constancy of the dust-scattered spectrum from the Homunculus. We extend previous work that showed a secular strengthening of P~Cygni absorptions by adding more orbital cycles to overcome temporary instabilities and by examining more atomic transitions. {\sc cmfgen} modeling of the primary wind shows that a time-decreasing mass-loss rate is not the best explanation for the observations. However, models with a `small' dissipating absorber in our line-of-site can explain both the increase in brightness and changes in the emission and P Cygni absorption profiles. If the spectral evolution is caused by the dissipating circumstellar medium, and not by intrinsic changes in the binary, the dynamical timescale to recover from the Great Eruption is much less than a century, different from previous suggestions.
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