Towards optical intensity interferometry for high angular resolution stellar astrophysics

TL;DR

This paper explores the potential of using Air Cherenkov Telescopes as optical intensity interferometers to achieve high angular resolution imaging of stars, enabling detailed surface studies and fundamental parameter measurements.

Contribution

It introduces a data analysis algorithm for image reconstruction from simulated intensity interferometry data and investigates the capabilities of future ACT arrays for stellar imaging.

Findings

Simulated data shows accurate imaging of stellar surfaces with hot and cool regions.

Demonstrated measurement of stellar angular diameters using intensity correlations.

Developed a prototype correlator system for intensity correlation measurements.

Abstract

Most neighboring stars are still detected as point sources and are beyond the angular resolution reach of current observatories. Methods to improve our understanding of stars at high angular resolution are investigated. Air Cherenkov telescopes (ACTs), primarily used for Gamma-ray astronomy, enable us to increase our understanding of the circumstellar environment of a particular system. When used as optical intensity interferometers, future ACT arrays will allow us to detect stars as extended objects and image their surfaces at high angular resolution. Optical stellar intensity interferometry (SII) with ACT arrays, composed of nearly 100 telescopes, will provide means to measure fundamental stellar parameters and also open the possibility of model-independent imaging. A data analysis algorithm is developed and permits the reconstruction of high angular resolution images from simulated SII data. The capabilities and limitations of future ACT arrays used for high angular resolution imaging are investigated via Monte-Carlo simulations. Simple stellar objects as well as stellar surfaces with localized hot or cool regions can be accurately imaged. Finally, experimental efforts to measure intensity correlations are expounded. The functionality of analog and digital correlators is demonstrated. Intensity correlations have been measured for a simulated star emitting pseudo-thermal light, resulting in angular diameter measurements. The StarBase observatory, consisting of a pair of 3 m telescopes separated by 23 m, is described.