Scintillation effect by gravitational wave on Quasars light curve

In this work we study the interaction of a gravitational wave from a binary star/blackhole with the electromagnetic wave from a distant quasar. While in the regime of geometric optics, the light bending due to this interaction is negligible, we show that the phase shifting on the wavefront of an electromagnetic wave can produce the interference pattern on the observer position. The effect is producing fringes from a distant quasar (with the wavelength of $\lambda_e$) by gravity wave (with the wavelength of $\lambda_g$) where the angular separation between the fringes is $\Delta\beta \sim \lambda_e/\lambda_g$. The relative motion of the observer, source of gravity wave and quasar results in a relative motion of observer through the interference pattern on the observer plane. The consequence of this fringe crossing is the modulation in the light curve of a quasar with the period of almost one month in radio wavelengths. The impact parameter of effective interaction between the electromagnetic wave and gravity wave is at least the wavelength of the gravity wave which results in the optical depth for the detection of this event for a given quasar to be larger than one. This is a new method of gravitational wave detection by the follow-up observations of quasars in millimetre wavelengths.