The Sydney University Stellar Interferometer: A Major Upgrade to Spectral Coverage and Performance

TL;DR

The paper details a major upgrade to the Sydney University Stellar Interferometer, enhancing spectral coverage and sensitivity through new systems and upgrades, enabling simultaneous observations and improved measurement accuracy.

Contribution

Introduction of a new beam-combination system and upgrades allowing simultaneous spectral observations and improved sensitivity in the interferometer.

Findings

Successful commissioning tests demonstrating system performance

Enhanced measurement accuracy of stellar angular diameters

Simultaneous dual-band spectral observations achieved

Abstract

A new beam-combination and detection system has been installed in the Sydney University Stellar Interferometer working at the red end of the visual spectrum (wavelength range 500-950 nm) to complement the existing blue-sensitive system (wavelength range 430-520 nm) and to provide an increase in sensitivity. Dichroic beam-splitters have been introduced to allow simultaneous observations with both spectral system, albeit with some restriction on the spectral range of the longer wavelength system (wavelength range 550-760 nm). The blue system has been upgraded to allow remote selection of wavelength and spectral bandpass, and to enable simultaneous operation with the red system with the latter providing fringe-envelope tracking. The new system and upgrades are described and examples of commissioning tests presented. As an illustration of the improvement in performance the measurement of the angular diameter of the southern F supergiant delta CMa is described and compared with previous determinations.