Mira局部发作性质量损失的证据
Evidence for localized onset of episodic mass loss in Mira
摘要：
我们报告多望远镜干涉测量的干涉光学望远镜阵列（IOTA），以提供图像的LPV米拉在H波段。这个波长区域非常适合研究质量损失，因为连续不透明度很低，可以在恒星大气层和包层中的很长路径上观察到发射。所观察到的vibrium是一致的一个简单的核心晕模型来代表中心对象和扩展的分子层，但此外，他们表现出实质性的不对称性。用图像重建软件分析表明，这种不对称性与局部吸收斑一致。观测到的不透明度暂时与小尘埃颗粒有关，这些小尘埃颗粒将在多年的喷射过程中大幅增长。空间信息以及推断的尘埃含量的云，已知的质量损失率，和喷射速度提供证据的脉动泵的扩展分子层。云可以被理解为一个空间上的局部区域的增强尘埃形成，非常接近脉动晕。观测到的质量损失可以由恒星周围的几个这样的活跃区域提供。这一结果为更好地理解AGB星大气中尘埃产生的团块提供了额外的线索。它与脉动和对流的组合在质量损失过程中起关键作用的场景兼容。
英文摘要：
We report Multi-telescope interferometric measurements taken with the Interferometric Optical Telescope Array (IOTA) to provide imagery of the LPV Mira in the H-band. This wavelength region is well suited to studying mass loss given the low continuum opacity, which allows for emission to be observed over a very long path in the stellar atmosphere and envelope. The observed visibilities are consistent with a simple core-halo model to represent the central object and the extended molecular layers but, in addition, they demonstrate a substantial asymmetry. An analysis with image reconstruction software shows that the asymmetry is consistent with a localized absorbing patch. The observed opacity is tentatively associated with small dust grains, which will grow substantially during a multi-year ejection process. Spatial information along with a deduced dust content of the cloud, known mass loss rates, and ejection velocities provide evidence for the pulsational pumping of the extended molecular layers. The cloud may be understood as a spatially local zone of enhanced dust formation, very near to the pulsating halo. The observed mass loss could be provided by several such active regions around the star. This result provides an additional clue for better understanding the clumpiness of dust production in the atmosphere of AGB stars. It is compatible with scenarios where the combination of pulsation and convection play a key role in the process of mass loss.
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