  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.
