Intensity Interferometer Results on Sirius with 0.25 m Telescopes

TL;DR

This study demonstrates that small, low-cost telescopes equipped with advanced photon detection technology can effectively measure stellar angular diameters through intensity interferometry, achieving results consistent with larger systems.

Contribution

It shows the feasibility of using small telescopes with modern detectors for intensity interferometry, enabling cost-effective measurements of stellar sizes.

Findings

Measured squared visibility of Sirius at 3.3 m baseline: 0.94±0.16

Achieved 7 sigma detection significance after 13.55 hours

Results closely match expected visibility, validating small telescope approach

Abstract

We present the successful measurement of the squared visibility of Sirius at a telescope separation of 3.3 m using small 0.25 m Newtonian-style telescopes in an urban backyard setting. The primary science goal for small-scale intensity interferometers has been to measure the angular diameters of stars. Recent advances in low jitter time-tagging equipment and Single Photon Avalanche Detectors have made the detection of second-order photon correlation signals feasible with small low-cost telescopes. Using Sirius as a target star, we observe a photon count rate of $\sim$1.9 Mcps per detector with matched 1.2 nm wide filters at 589.3 nm and measured the spatial squared visibility at a telescope separation of 3.3 m to be $|V_{12}(3.3\text{m})|^2 = 0.94\pm0.16$. The measured detection significance is $\sim7 \sigma$ after 13.55 h of integration. The uncertainty in the measured visibility includes uncertainty in the instrument response function.The squared visibility agrees closely with the expected value of $0.94\pm0.01$. These results demonstrate that using small low-cost telescopes is feasible for intensity interferometry of bright stars. This enables a simple scaling in sensitivity by further realistic improvements in the instrument response jitter as well as increasing both the number of spectral bands and the number of telescopes towards systems capable of resolving objects such as quasars, white dwarfs, and galactic Cepheid variable stars.