The Challenges of Coronagraphic Astrometry
The Challenges of Coronagraphic Astrometry
复制标题
日冕天体测量的挑战
DOI：
10.1086/506339
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
L. Newburgh
中科院分区：
文献类型：
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作者：
A. Digby;S. Hinkley;B. Oppenheimer;A. Sivaramakrishnan;J. Lloyd;M. Perrin;Lewis C. Roberts Jr.;R. Soummer;D. Brenner;R. Makidon;M. Shara;J. Kuhn;J. Graham;P. Kalas;L. Newburgh
日冕仪与自适应光学相结合，提供了一种从地面对附近恒星的微弱伴星进行成像的有效手段。然而，来自这样一个系统的图像是复杂的，需要在行星或圆盘能够在宿主恒星的眩光下被探测到之前得到充分的表征和理解。利用Lyot项目日冕仪的数据，我们研究了在衍射有限的日冕图像中进行天文测量的困难，并考虑了确定掩星精确位置的主要问题。我们演示了当恒星偏离光轴时，图像结构是如何变化的，并展示了即使很小的偏移量（0.05λ/D或5 mas）也会在图像中产生假源。我们从质心测量、仪器反馈和点扩散函数对称性分析等方面考虑了确定恒星位置的方法，并得出内部测量是最有效的方法。
A coronagraph in conjunction with adaptive optics provides an effective means to image faint companions of nearby stars from the ground. The images from such a system are complex, however, and need to be fully characterized and understood before planets or disks can be detected against the glare from the host star. Using data from the Lyot Project coronagraph, we investigate the difficulties of astrometric measurements in diffraction-limited coronagraphic images and consider the principal problem of determining the precise location of the occulted star. We demonstrate how the image structure varies when the star is decentered from the optical axis and show how even small offsets (0.05λ/D or 5 mas) give rise to false sources in the image. We consider methods of determining the star position from centroiding, instrument feedback, and analysis of point-spread function symmetry and conclude that internal metrology is the most effective technique.