Temporal intensity interferometry: photon bunching in three bright stars

• Published in: Monthly notices of the Royal Astronomical Society 2017-12, Vol.472 (4), p.4126-4132
• Main Authors: Guerin, W., Dussaux, A., Fouché, M., Labeyrie, G., Rivet, J.-P., Vernet, D., Vakili, F., Kaiser, R.
• Format: Article
• Language: English
• Subjects: Astrophysics; Avalanche diodes; Bunching; Correlation analysis; Focal plane; Instrumentation and Methods for Astrophysic; Interferometry; Photodiodes; Sciences of the Universe; Telescopes; Wavelengths
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stx2143

Abstract We report the first intensity correlation measured with starlight since the historical experiments of Hanbury Brown and Twiss. The photon bunching g(2)(τ, r = 0), obtained in the photon-counting regime, was measured for three bright stars: α Boo, α CMi and β Gem. The light was collected at the focal plane of a 1-m optical telescope, transported by a multi-mode optical fibre, split into two avalanche photodiodes and correlated digitally in real time. For total exposure times of a few hours, we obtained contrast values around 2 × 10−3, in agreement with the expectation for chaotic sources, given the optical and electronic bandwidths of our set-up. Comparing our results with the measurement of Hanbury Brown et al. for α CMi, we argue for the timely opportunity to extend our experiments to measuring the spatial correlation function over existing and/or foreseen arrays of optical telescopes diluted over several kilometres. This would enable microarcsec long-baseline interferometry in the optical, especially in the visible wavelengths, with a limiting magnitude of 10.