The Interstellar Medium as a Gravity Wave Detector

Abstract

An observer, situated several thousand light-years away from a radio pulsar, finds himself embedded in the diffraction pattern resulting from the propagation of the radio waves through the irregular interstellar medium. The observer's movement relative to the pattern causes an apparent scintillation of the pulsar. A binary star, situated close to the pulsar's line-of-sight, is generating relatively strong gravity waves. The rays originating from the pulsar experience a tiny periodic deflection due to the gravity waves produced by the binary star. This deflection displaces the diffraction pattern laterally in a manner that is familiar from refractive interstellar scintillation, except that this gravity wave effect is not dispersive. The displacement has the same period as the gravity waves. Its amplitude equals the product of the tiny deflection angle and the large distance from the binary star to the observer. This periodic displacement can reach a few hundred kilometers, which can be comparable to the size of the features in the diffractive pattern. Thus, there seems to be a possibility that the exceedingly faint gravity waves can manifest themselves macroscopically. Observationally, the end effect could be a substantial, deterministic alteration of the scintillation time structure.