High angular resolution observations at optical wavelengths provide valuable insights into stellar astrophysics^1,2, and enable direct measurements of fundamental stellar parameters^3,4 and the probing of stellar atmospheres, circumstellar disks⁵, the elongation of rapidly rotating stars⁶ and the pulsations of Cepheid variable stars⁷. The angular size of most stars is of the order of one milliarcsecond or less, and to spatially resolve stellar disks and features at this scale requires an optical interferometer using an array of telescopes with baselines on the order of hundreds of metres. We report on the implementation of a stellar intensity interferometry system developed for the four VERITAS imaging atmospheric Cherenkov telescopes. The system was used to measure the angular diameter of the two sub-milliarcsecond stars β Canis Majoris and ϵ Orionis with a precision of greater than 5%. The system uses an offline approach in which starlight intensity fluctuations that are recorded at each telescope are correlated post observation. The technique can be readily scaled onto tens to hundreds of telescopes, providing a capability that has proven technically challenging to the current generation of optical amplitude interferometry observatories. This work demonstrates the feasibility of performing astrophysical measurements using imaging atmospheric Cherenkov telescope arrays as intensity interferometers and shows the promise for integrating an intensity interferometry system within future observatories such as the Cherenkov Telescope Array.

在光学波长上的高角分辨率观测结果可提供对恒星天体物理学^1,2的宝贵见解，并能够直接测量恒星基本参数^3,4，并探测恒星大气，星际盘⁵，快速旋转恒星的伸长⁶以及恒星的脉动造父变星⁷。大多数恒星的角大小约为1毫秒或更小，并且要在空间上解析恒星盘，并且要在这种尺度下分辨特征，就需要使用光学干涉仪，其使用一系列望远镜，其基线约为数百米。我们报告了为四个VERITAS成像大气Cherenkov望远镜开发的恒星强度干涉测量系统的实施情况。该系统被用于测量两个子milliarcsecond分的角直径β大犬座和εOrionis的精度大于5％。该系统使用离线方法，其中在每个望远镜上记录的星光强度波动与观测后相关。该技术可以很容易地缩放到数十到数百个望远镜上，提供的功能已被证明对当前一代的光学幅度干涉仪观测站具有技术挑战。这项工作证明了使用大气奇伦科夫望远镜阵列成像作为强度干涉仪进行天体测量的可行性，并显示了将强度干涉测量系统集成到诸如契伦科夫望远镜阵列等未来观测站中的希望。