Single-photon intensity interferometry (SPIIFY): Utilizing available telescopes

One of the main scientific goals of optical interferometers is to measure the angular diameters of stars. These measurements, combined with precise distance measurements, such as those from the upcoming Gaia satellite, can provide improved constraints on stellar linear diameters and effective temperature. We describe a modular intensity interferometer system using commercially available single-photon detectors. We present our calculations on the sensitivity and uv-plane coverage using these modules mounted on existing telescopes on Kitt Peak, Arizona. Determining accurate stellar properties is important for testing models of stellar evolution as well as for deriving physical properties of transiting exoplanets. Our simulations indicate that we should be able to measure stellar diameters of bright stars with AB magnitude ≤6 with a precision of ≥5 per cent in a single night of observation.