Time delay induced by plasma in strong lens systems

If the gravitational lens is surrounded by non-homogeneous plasma, in addition to the vacuum gravitational deflection, chromatic refraction occurs. Also, the speed of signal propagation decreases compared to a vacuum. In this article, we investigate analytically the time delay in the case of gravitational lensing in plasma, focusing on strong lens systems. We take into account the following contributions: geometric delay due to trajectory bending in the presence of both gravity and plasma; potential delay of the ray in the gravitational field of the lens; dispersion delay in the plasma due to decrease in the speed of light signal in the medium. We consider the singular isothermal sphere as a model of a gravitational lens and the arbitrary spherically symmetric distribution of surrounding plasma. For this scenario, plasma corrections for the time delay between two images are found in a compact analytical form convenient for estimates.

Automated summary

In this article, we analytically investigate the time delay in the case of gravitational lensing in plasma, focusing on strong lens systems. Various contributions including geometric delay, potential delay, and dispersion delay are taken into account. We consider the singular isothermal sphere as a model for the gravitational lens and the arbitrary spherically symmetric distribution of surrounding plasma. Plasma corrections for the time delay between two images are derived in a compact analytical form convenient for estimates.