Precision Measurement of Stellar Sizes and Circumstellar Material with 10 Micron Interferometry and Narrow Frequency Bandwidths

利用 10 微米干涉仪和窄频带精确测量恒星尺寸和星周材料

• 批准号: 0707233
• 负责人: Charles Townes
• 金额: --
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-15 至 2008-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0707233&HistoricalAwards=false
• 关键词: Precision; Measurement; Stellar; Sizes; Circumstellar

An observational program using Berkeley's unique Infrared Spatial Interferometer (ISI) with three movable 60 inch telescopes will be carried out to obtain high-resolution images of evolved late-type stars. This will include interferometric measurement of the diameters of old stars in narrow spectral regions at mid-infrared (11 micron) wavelengths chosen to avoid spectral lines due to gases in the immediate atmospheres of stars, careful examination of the shapes of stars using these baselines in different directions and with phase closure, and narrow-band measurements directly on spectral lines to determine the spatial distribution of such gases around the stars. Some mapping of dust emitted by stars using multiple baselines and phase also may be made, but measurement of stellar disks and shapes will be emphasized.Baselines available to the ISI range from four to approximately 75 meters and allow accurate measurements of old stars as well as the dust and gas distributions around them. Measurements in the mid-IR and with narrow bandwidths minimize the distortions in apparent size due to limb darkening or to spectra of surrounding gas. The ISI system uses heterodyne detection which has a bandwidth of about 0.2/cm; furthermore the resulting signals can be filtered to obtain arbitrarily narrow spectral widths. Stellar size measurements to a precision of 1% or better have been demonstrated. Phase closure measurements are made to an accuracy of one degree, allowing nearly complete Fourier analysis of intensity patterns, including asymmetries. The observing campaign will emphasize the examination of possible deviations from sphericity of Miras and red giants, and changes in stellar size with time and phase of stellar oscillation.Previous ISI measurements have shown movements of dust clouds surrounding late-type stars as well as deviations of the clouds from spherical symmetry. During the coming year focus will be placed on measurements of the stars themselves. The third movable telescope recently installed on Mt.Wilson functions well, and increases the visibility measurements by a factor of three as well as allowing accurate phase closure measurements. This allows interferometry with three baselines of various orientations to be measured simultaneously, along with phase closure. Asymmetries and irregular timing in emission of material by old stars appear common, but the asymmetries of stars themselves are not yet known.The overall goals of this project are to provide a substantial increase in our knowledge of the characteristics of old stars through the detailed new measurements which are made possible via ISI and the development of interferometric technology. Opportunities will be provided for the training of young scientists (from undergraduates to postdocs) in optics, electronics, computer control of systems, telescope operation, data analysis, and scientific interpretation.

将利用伯克利独特的红外空间干涉仪（ISI）和三个可移动的60英寸望远镜进行一项观测方案，以获得演化的晚型恒星的高分辨率图像。 这将包括在中红外窄光谱区对老恒星直径的干涉测量（11微米）波长的选择，以避免光谱线，由于气体在直接大气层的恒星，仔细检查的形状，恒星使用这些基线在不同的方向和相位关闭，以及直接在光谱线上进行窄带测量，以确定恒星周围这种气体的空间分布。 利用多个基线和相位也可以绘制一些恒星释放的尘埃图，但重点是测量恒星盘和形状。ISI可用的基线范围从4米到大约75米，可以精确测量老恒星以及它们周围的尘埃和气体分布。 在中红外和窄带宽的测量最大限度地减少了由于临边变暗或周围气体的光谱在表观尺寸上的失真。 ISI系统使用具有约0.2/cm的带宽的外差检测;此外，所得到的信号可以被滤波以获得任意窄的频谱宽度。 恒星尺寸测量的精度为1%或更好已经得到证明。 相位闭合测量的精度为一度，允许几乎完整的傅立叶分析的强度模式，包括不对称性。 观测活动将着重研究Miras和红巨星可能偏离球形的情况，以及恒星大小随时间和恒星振荡相位的变化。ISI以前的测量显示了晚型恒星周围尘埃云的运动以及云偏离球形对称的情况。 在接下来的一年里，重点将放在恒星本身的测量上。最近安装在威尔逊山的第三台可移动望远镜运行良好，将能见度测量值提高了三倍，并实现了准确的相位闭合测量。 这允许同时测量具有不同取向的三个基线的干涉测量，沿着相位闭合。 老恒星物质发射的不对称性和不规则定时似乎很常见，但恒星本身的不对称性尚不清楚，该项目的总体目标是通过ISI和干涉测量技术的发展，通过详细的新测量，大幅度增加我们对老恒星特征的了解。 将为青年科学家（从本科生到博士后）提供光学、电子学、系统计算机控制、望远镜操作、数据分析和科学解释方面的培训机会。