Temporal Evolution of Coronagraphic Dynamic Range and Constraints on Companions to Vega
Temporal Evolution of Coronagraphic Dynamic Range and Constraints on Companions to Vega
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DOI：
10.1086/509063
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发表时间：
2006-09
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通讯作者：
S. Hinkley;B. Oppenheimer;R. Soummer;A. Sivaramakrishnan;Lewis C. Roberts Jr.;J. Kuhn;R. Makidon;M. Perrin;J. Lloyd;K. Kratter;D. Brenner
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作者：
S. Hinkley;B. Oppenheimer;R. Soummer;A. Sivaramakrishnan;Lewis C. Roberts Jr.;J. Kuhn;R. Makidon;M. Perrin;J. Lloyd;K. Kratter;D. Brenner
直接探测邻近恒星伴星的主要障碍是主星压倒性的亮度。目前采用自适应光学 (AO) 和日冕术相结合的仪器通常可以探测到恒星 2 英寸范围内亮度约 104-105 倍的物体。相关散斑噪声是限制这种高对比度成像的最大障碍之一。我们通过位于夏威夷哈雷阿卡拉的 3.63 m AEOS 望远镜获得了一系列 284 8 s、AO 校正、日冕掩星 H 波段图像。该数据集对于研究散斑噪声的时间行为来说是独一无二的，并且代表了首次以定量方式对高度校正的冠状 AO 图像进行此类研究。我们发现数据中的散斑图案在位置和时间上都高度稳定。这是因为 AO 系统在仪器波前误差占主导地位的水平上校正了对恒星波前的干扰。因此，我们发现仅增加曝光时间并不能显着提高检测限。然而，通过减去两个旋转框架（望远镜光瞳框架和可变形镜框架）中的静态/准静态散斑，我们能够将动态范围提高 1.5-2 mag。对于任何使用日冕摄影术和高阶 AO 的程序来说，散斑的高度稳定性都将存在。此外，根据我们的数据，我们能够将任何所谓的织女星伴星的质量限制在 8 个天文单位时小于约 45MJ，在 16 个天文单位时小于约 30MJ，这些半径以前没有在这些灵敏度下探测过。
The major obstacle to the direct detection of companions to nearby stars is the overwhelming brightness of the host star. Current instruments employing the combination of adaptive optics (AO) and coronagraphy can typically detect objects within 2'' of the star that are ~104-105 times fainter. Correlated speckle noise is one of the biggest obstacles limiting such high-contrast imaging. We have obtained a series of 284 8 s, AO-corrected, coronagraphically occulted H-band images of the star Vega at the 3.63 m AEOS telescope located on Haleakala, Hawaii. This data set is unique for studying the temporal behavior of speckle noise and represents the first time such a study on highly corrected coronagraphic AO images has been carried out in a quantitative way. We find the speckle pattern to be highly stable in both position and time in our data. This is due to the fact that the AO system corrects disturbances to the stellar wave front at the level where the instrumental wave front errors dominate. Because of this, we find that our detection limit is not significantly improved simply with increased exposure time alone. However, we are able to improve our dynamic range by 1.5-2 mag through subtraction of static/quasi-static speckles in two rotating frames: the telescope pupil frame and the deformable mirror frame. The highly stable nature of speckles will exist for any program using coronagraphy and high-order AO. Furthermore, from our data, we are able to constrain the mass of any purported companion to Vega to be less than ~45MJ at 8 AU and less than ~30MJ at 16 AU, radii not previously probed at these sensitivities.