Keck孔径掩蔽实验：6个Mira变星的多波长观测
The Keck Aperture Masking Experiment: Multi-Wavelength Observations of 6 Mira Variables
摘要：
在1997年1月至2004年9月的一项广泛的观测计划中，利用孔径掩模技术测量了6个富氧Mira型长周期变星的角直径。这些数据集跨越了观测对象的许多脉动周期，是迄今为止对Mira星进行的多波长、多历元干涉角直径测量的最大研究。校准的能见度数据的o Cet，R狮子座，R Cas，W Hya，chi Cyg和R Hya的拟合使用统一的磁盘亮度分布模型，以方便历元，波长之间的比较，并与现有的数据和理论模型。角直径的变化作为波长和时间的函数进行了研究，并检测到循环直径变化的所有对象在我们的样本。这些变化被认为是源于这些恒星不同层的密度和温度随时间的变化（从而改变分子的不透明度）。在现有的理论模型的背景下，这些对象之间的行为的相似性和差异进行了分析和讨论。此外，我们提出了与时间相关的3.08微米角直径测量，首次探测这些可能形成灰尘的区域，这些区域显示出不可预见的尺寸，并且与本研究中显示的其他NIR层一致。在这项研究中，S型Mira chi Cyg与M型Miras相比表现出显着不同的行为。
英文摘要：
The angular diameters of six oxygen rich Mira-type long-period variables have been measured at various near-infrared (NIR) wavelengths using the aperture masking technique in an extensive observing program from 1997 Jan to 2004 Sep. These data sets span many pulsation cycles of the observed objects and represent the largest study of multi-wavelength, multi-epoch interferometric angular diameter measurements on Mira stars to date. The calibrated visibility data of o Cet, R Leo, R Cas, W Hya, chi Cyg and R Hya are fitted using a uniform disk brightness distribution model to facilitate comparison between epochs, wavelengths and with existing data and theoretical models. The variation of angular diameter as a function of wavelength and time are studied, and cyclic diameter variations are detected for all objects in our sample. These variations are believed to stem from time-dependent changes of density and temperature (and hence varying molecular opacities) in different layers of these stars. The similarities and differences in behaviour between these objects are analyzed and discussed in the context of existing theoretical models. Furthermore, we present time-dependent 3.08 micron angular diameter measurements, probing for the first time these zones of probable dust formation, which show unforeseen sizes and are consistently out of phase with other NIR layers shown in this study. The S-type Mira chi Cyg exhibits significantly different behaviour compared to the M-type Miras in this study.
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