Stellar Intensity Interferometry: Imaging capabilities of air Cherenkov telescope arrays

TL;DR

This paper explores the potential of large air Cherenkov telescope arrays for stellar imaging through intensity interferometry, demonstrating that high-resolution images of stars can be reconstructed with sufficient coverage and phase retrieval techniques.

Contribution

It demonstrates the feasibility of stellar imaging at sub-milli-arcsecond resolution using existing telescope arrays with simulated data and phase recovery methods.

Findings

Uncertainty in stellar radius reconstruction is a few percent after hours of exposure.

Imaging of complex stellar images at sub-milli-arc-second scale is achievable.

Large telescope arrays can be effectively used for high-resolution stellar imaging.

Abstract

Sub milli-arcsecond imaging in the visible band will provide a new perspective in stellar astrophysics. Even though stellar intensity interferometry was abandoned more than 40 years ago, it is capable of imaging and thus accomplishing more than the measurement of stellar diameters as was previously thought. Various phase retrieval techniques can be used to reconstruct actual images provided a sufficient coverage of the interferometric plane is available. Planned large arrays of Air Cherenkov telescopes will provide thousands of simultaneously available baselines ranging from a few tens of meters to over a kilometer, thus making imaging possible with unprecedented angular resolution. Here we investigate the imaging capabilities of arrays such as CTA or AGIS used as Stellar Intensity Interferometry receivers. The study makes use of simulated data as could realistically be obtained from these arrays. A Cauchy-Riemann based phase recovery allows the reconstruction of images which can be compared to the pristine image for which the data were simulated. This is first done for uniform disk stars with different radii and corresponding to various exposure times, and we find that the uncertainty in reconstructing radii is a few percent after a few hours of exposure time. Finally, more complex images are considered, showing that imaging at the sub-milli-arc-second scale is possible.