Electron scintillation in gravitationally lensed images of astrophysical radio sources

The combined effect of the gravitational lensing of astrophysical radio sources by a point mass and the propagation of the radiation through a statistically varying medium of free electrons is explored. Explicit expressions are obtained in the limit of weak scintillation, and the thin screen approximation is utilized throughout. The chief specific results are the following. The limiting angular size of the source to cause scintillation is increased by the amplification factor for the luminosity of the image, the fluctuations due to electron scintillation are different for the two images, and the amplitude of these fluctuations varies with the lens-source-observer geometry in a manner similar to a diffraction pattern. In practice, the observation of scintillation of radio sources is limited by the requirement that they be quite small. This study is related to the possibilities for detection of nonluminous matter in astrophysics in the form of stellar and planetary mass objects. 15 references