PRECISION MEASUREMENT OF STELLAR SIZES AND CIRCUMSTELLAR MATERIAL WITH 10 MICRON INTERFEROMETRY AND NARROW FREQUENCY BANDWIDTHS

伯克利红外空间干涉仪是一个独特的系统，由三个1.65米的望远镜组成。威尔逊天文台。它的基线范围从4米到大约75米，能够达到20毫角秒的分辨率。该系统采用外差检测，带宽为0.2/cm，可对产生的信号进行滤波，获得任意窄的频谱宽度。最近增加的第三台望远镜使相位闭合测量达到了1度的精度，这使得对包括不对称在内的强度模式的近乎完整的傅里叶分析。使用干涉仪将继续进行进化的晚型恒星的观测计划。这些恒星的大小和选定的相关特征(周围的尘埃分布和不对称性、水蒸气包层等)窄带宽能力将允许避开或选择周围气体的原子和分子谱线，从而产生可靠和真实的恒星大小等特征。观测将跟踪日冕米拉变星的大小随相位的变化，并检查可能偏离米拉和红巨星球形度的情况。之前用干涉仪进行的研究已经显示了晚型恒星周围尘埃云的运动，以及尘埃云偏离球对称的情况。对这些变化的研究将继续提供关于恒星周围尘埃云运动的信息，并由此和多普勒测量确定距离。这里的工作将为年轻科学家(一名博士后研究助理)和学生(两名研究生和本科生)提供培训，他们将有实际机会学习光学、电子学、计算机控制系统、数据分析和科学解释。干涉测量和仪器测量是天文学界高度重视的两个领域，对下一代仪器建造者的教育对该领域的持续成功至关重要。

ABSTRACTThe Berkeley Infrared Spatial Interferometer is a unique system of three 1.65-metertelescopes located at the Mt. Wilson Observatory. Its baselines range from 4 toapproximately 75 meters and it is capable of 20 milliarcsecond resolution. The systemuses heterodyne detection with a bandwidth of 0.2/cm and the resulting signals can befilters to obtain arbitrarily narrow spectral widths. The recent addition of a third telescopehas allowed phase closure measurements to an accuracy of 1 degree, which allows nearlycomplete Fourier analysis of intensity patterns, including asymmetries.An observing program of evolved late-type stars will be continued using theinterferometer. The sizes of such stars and select associated features (surrounding dustdistributions and asymmetries, water vapor envelopes, etc.) will be directly measured.The narrow bandwidth capability will allow the atomic and molecular spectral lines ofsurrounding gas to be avoided or selected yielding, among other characteristics, reliableand realistic stellar sizes. The observations will follow the changes in size of prominentMira variable stars as a function of phase and examine possible departures fromsphericity of Miras and red giants. Previous studies with the interferometer have shownmovements of dust clouds surrounding late-type stars as well as deviations of the cloudsfrom spherical symmetry. Studies of these variations will be continued to provideinformation on the motion of dust clouds around stars, and from this and Dopplermeasurements, also a determination of distances.The work here will provide training for young scientists (a postdoctoral researchassociate) and students (2 graduate students as well as undergraduates) who will havehands-on opportunities to learn optics, electronics, computer control systems, dataanalysis, and scientific interpretation. Interferometry and instrumentation are two areas ofhigh priority for the astronomical community and the education of the next generation ofinstrument builders is critical the field's continued success.