High angular resolution observations at optical wavelengths provide valuable insights into stellar astrophysics, and enable direct measurements of fundamental stellar parameters and the probing of stellar atmospheres, circumstellar disks, the elongation of rapidly rotating stars and the pulsations of Cepheid variable stars. 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.
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Implementation of an intensity interferometry system on the StarBase observatory
A modern implementation of a stellar intensity interferometry (SII) system on an array of large optical telescopes would be a highly valuable complement to the current generation of optical amplitude interferometers. The SII technique allows for observations at short optical wavelengths (U/B/V bands) with potentially dense (u,v) plane coverage. We describe a complete SII system that is used to measure the spatial coherence of a laboratory source which exhibits signal to noise ratios comparable to actual stellar sources. A novel analysis method, based on the correlation measurements between orthogonal polarization states, was developed to remove unwanted effects of spurious correlations. Our system is currently being tested in night sky observations at the StarBase Observatory (Grantsville, Utah) and will soon be ported to the VERITAS (Amado, AZ) telescopes. The system can readily be integrated with current optical telescopes at minimal cost. The work here serves as a technological pathfinder for implementing SII on the future Cherenkov Telescope Array.
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- NSF-PAR ID:
- 10088153
- Date Published:
- Journal Name:
- Proc. SPIE 10701 Optical and Infrared Interferometry and Imaging IV
- Volume:
- 107010W
- Page Range / eLocation ID:
- 16
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1117/12.2312716
