Achromatic interfero coronagraphy I. Theoretical capabilities for ground-based observations
Achromatic interfero coronagraphy I. Theoretical capabilities for ground-based observations
复制标题
消色差干涉日冕术 I. 地面观测的理论能力
DOI：
10.1051/aas:2000120
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发表时间：
2000
期刊：
影响因子：
--
通讯作者：
Y. Rabbia
中科院分区：
文献类型：
--
作者：
P. Baudoz;Y. Rabbia
我们提出了一个概念，致力于检测微弱的同伴或其他形态的成分，在附近的星星通过日冕照相术。基本上，这种方法依赖于相消干涉，以便实现轴上点状源的消光。在这方面，报告的概念是一个调零干涉仪设计的工作与一个单一的光圈。我们的日冕有两个特征，即消色差和近感。非色度允许灵活选择工作波长和大光谱带宽。近距离传感提供了在中心源周围进行探测的能力，比现有的日冕仪所能达到的要近得多。虽然我们的概念最初是设计用于天基仪器，但本文的目标是通过理论分析表明，它可以在配备自适应光学的地面大型望远镜上发挥作用。这尤其涉及到其他日冕仪无法达到的水平（优于方向限制）的近距离感应能力。关于检测的基本限制起源于残余波前畸变，其效应在这里使用自适应光学的形式主义来描述。在本文中的原则，通用的设置和局限性进行了简要回顾。文中给出了大气视宁度影响和自适应光学应用的代数推导。理论预期的探测能力的地面操作，表明检测的伴星比中央星星的6个星等的信噪比（SNR）为5似乎是一个合理的目标，从原始数据，与4米级的望远镜在相当普通的条件下，与适度的积分时间。自适应光学的不断进步，使得在类似条件下可以达到12的量级。
We present a concept dedicated to the detection of faint companions or other morphological components in the neighbouring of a star by means of coronagraphy. Basically this method relies on destructive interferences so as to achieve extinction of the on-axis point-like source. In this regard the reported concept is a nulling interferometer designed for work with a single aperture. Two features are specic to our coronagraph, namely achromaticity and close-sensing. Achromaticity allows flexible choice of a working wavelength and of a large spectral bandwidth. Close-sensing provides the ability to explore around the central source signicantly closer than can be achieved by existing coronographs. Though our concept has been initially devised for use on a space-based instrument it is the goal of this paper to show by theoretical analysis that it can be ecient and powerful on ground-based large telescopes equipped with adaptive optics. This especially regards close-sensing capabilities at a level (better than diraction limit) un- reachable by other coronagraphs. The essential limitation regarding detection originates in residual wavefront distor- tions whose eects are described here using the formalism of adaptive optics. In this paper the principle, the generic set-up and the limitations are briefly recalled. Algebraic derivations re- garding the eect of atmospheric seeing and the use of adaptive optics are given. Theoretical expected detection capabilities for ground-based operation are derived, show- ing that detection of a companion fainter than the central star by 6 magnitudes with a Signal to Noise Ratio (SNR) of 5 appears to be a reasonable goal from raw data, with a 4-meter class telescope in rather ordinary conditions and with modest integration times. On-going progress in adap- tive optics, make it conceivable to reach magnitude dier- ences of 12 under similar conditions.