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Stellar intensity interferometry: Prospects for sub-milliarcsecond optical imaging

机译：恒星强度干涉测量法：亚毫秒级光学成像的前景

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摘要

Using kilometric arrays of air Cherenkov telescopes at short wavelengths, intensity interferometry may increase the spatial resolution achieved in optical astronomy by an order of magnitude, enabling images of rapidly rotating hot stars with structures in their circumstellar disks and winds, or mapping out patterns of nonradial pulsations across stellar surfaces. Intensity interferometry (once pioneered by Hanbury Brown and Twiss) connects telescopes only electronically, and is practically insensitive to atmospheric turbulence and optical imperfections, permitting observations over long baselines and through large air-masses, also at short optical wavelengths. The required large telescopes (～10 m) with very fast detectors (～ns) are becoming available as the arrays primarily erected to measure Cherenkov light emitted in air by particle cascades initiated by energetic gamma rays. Planned facilities (e.g., CTA, Cherenkov Telescope Array) envision many tens of telescopes distributed over a few square km. Digital signal handling enables very many baselines (from tens of meters to over a kilometer) to be simultaneously synthesized between many pairs of telescopes, while stars may be tracked across the sky with electronic time delays, in effect synthesizing an optical interferometer in software. Simulated observations indicate limiting magnitudes around m_v = 8, reaching angular resolutions ～30 μarcsec in the violet. The signal-to-noise ratio favors high-temperature sources and emission-line structures, and is independent of the optical passband, be it a single spectral line or the broad spectral continuum. Intensity interferometry directly provides the modulus (but not phase) of any spatial frequency component of the source image; for this reason a full image reconstruction requires phase retrieval techniques. This is feasible if sufficient coverage of the interferometric (u, v)-plane is available, as was verified through numerical simulations. Laboratory and field experiments are in progress; test telescopes have been erected, intensity interferometry has been achieved in the laboratory, and first full-scale tests of connecting large Cherenkov telescopes have been carried out. This paper reviews this interferometric method in view of the new possibilities offered by arrays of air Cherenkov telescopes, and outlines observational programs that should become realistic already in the rather near future.
机译：通过使用短波长的空中Cherenkov望远镜的千米阵列，强度干涉测量法可以将光学天文学中获得的空间分辨率提高一个数量级，从而使快速旋转的热恒星的图像具有其星圆盘和风中的结构，或者绘制出非径向模式横跨星状表面的脉动。强度干涉测量法（由Hanbury Brown和Twiss率先采用）仅通过电子方式连接望远镜，并且实际上对大气湍流和光学缺陷不敏感，因此可以在较长的基线和较大的空气质量（也可以在短波长）下进行观察。所需的大型望远镜（〜10 m）具有非常快的探测器（〜ns），这是因为这些阵列主要是用来测量由高能伽马射线引发的粒子级联在空气中发射的切伦科夫光的阵列。计划中的设施（例如CTA，切伦科夫望远镜阵列）设想了数十个分布在几平方公里上的望远镜。数字信号处理可以在许多对望远镜之间同时合成非常多的基线（从几十米到一公里以上），同时可以通过电子延时在天空中跟踪恒星，实际上是在软件中合成了光学干涉仪。模拟的观测结果表明，在m_v = 8附近的极限幅值在紫罗兰色中达到了约30μarcsec的角分辨率。信噪比有利于高温源和发射线结构，并且与光通带无关，无论是单谱线还是宽谱连续体。强度干涉测量法直接提供源图像的任何空间频率分量的模量（而不是相位）；因此，完整的图像重建需要相位检索技术。如果有足够的干涉测量（u，v）平面覆盖，则这是可行的，这已通过数值模拟进行了验证。正在进行实验室和野外实验；已经建立了测试望远镜，在实验室中实现了强度干涉测量，并且已经进行了连接大型切伦科夫望远镜的首次全面测试。鉴于空中Cherenkov望远镜阵列提供的新可能性，本文回顾了这种干涉测量方法，并概述了在不久的将来应该已经成为现实的观测程序。

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  • 来源
    《New astronomy reviews》 |2012年第5期|143-167|共25页
  • 作者

    Dainis Dravins; Stephan LeBohec; Hannes Jensen; Paul D. Nunez;

  • 作者单位

    Lund Observatory, Box 43, SE-22100 Lund, Sweden;

    Department of Physics and Astronomy, The University of Utah, 115 South 1400 East, Salt Lake City, UT 84112-0830, USA;

    Lund Observatory, Box 43, SE-22100 Lund, Sweden,Department of Astronomy and Oskar Klein Centre, Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden;

    Department of Physics and Astronomy, The University of Utah, 115 South 1400 East, Salt Lake City, UT 84112-0830, USA;

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