Intensity interferometry for observation of dark objects

TL;DR

This paper explores how intensity interferometry can detect and analyze dark, absorptive objects like planets occluding stars by measuring perturbations in the covariance function, offering a complementary method to direct imaging.

Contribution

It introduces a novel application of intensity interferometry for observing dark objects and analyzes the key parameters affecting measurement sensitivity and accuracy.

Findings

Perturbations in covariance function reveal object presence and orientation.

Magnitude of covariance perturbation equals intensity variation caused by the object.

Differential measurements may be necessary for faint signals in astronomy.

Abstract

We analyze an intensity interferometry measurement carried out with two point-like detectors facing a distant source (e.g., a star) that may be partially occluded by an absorptive object (e.g., a planet). Such a measurement, based on the perturbation of the observed covariance function due to the object's presence, can provide information of the object complementary to a direct optical intensity measurement. In particular, one can infer the orientation of the object's transient trajectory. We identify the key parameters that impact this perturbation and show that its magnitude is equal to the magnitude of the intensity variation caused by the same object. In astronomy applications, this value may be very small, so a differential measurement may be necessary. Finally, we discuss the signal-to-noise ratio that may be expected in this type of measurement.