Spatial intensity interferometry on three bright stars

TL;DR

This paper reports the first spatial intensity interferometry measurements of stars since the 1970s, utilizing modern photon-counting detectors to measure correlations between light collected by two telescopes, demonstrating the technique's viability and limitations.

Contribution

It presents the first recent measurements of stellar intensity interferometry using advanced detectors, confirming the method's effectiveness and exploring its constraints with different stars.

Findings

Reliable visibility measurements achieved with 4-hour exposures.

Contrast loss observed on alpha Aur due to its binary nature.

Validation of modern photon-counting detectors for stellar interferometry.

Abstract

The present articlereports on the first spatial intensity interferometry measurements on stars since the observations at Narrabri Observatory by Hanbury Brown et al. in the 1970's. Taking advantage of the progresses in recent years on photon-counting detectors and fast electronics, we were able to measure the zero-time delay intensity correlation $g^{(2)}(\tau = 0, r)$ between the light collected by two 1-m optical telescopes separated by 15 m. Using two marginally resolved stars ($\alpha$ Lyr and $\beta$ Ori) with R magnitudes of 0.01 and 0.13 respectively, we demonstrate that 4-hour correlation exposures provide reliable visibilities, whilst a significant loss of contrast is found on alpha Aur, in agreement with its binary-star nature.