Intensity and polarization of radiation reflected from accretion disc

TL;DR

This paper analyzes how the polarization of radiation reflected from accretion discs depends on the aperture angle and optical thickness, revealing a polarization switch at a 70-degree angle.

Contribution

It provides a detailed study of polarization dependence on aperture angle for both optically thick and thin accretion discs, identifying a polarization orientation transition.

Findings

Polarization orientation switches at a 70-degree aperture angle for optically thick discs.

Reflected radiation from optically thin discs always has electric field oscillations parallel to the disc normal.

The polarization behavior depends on the aperture angle and optical thickness of the disc.

Abstract

We consider the reflection of non-polarized radiation from the point-like sources above the accretion discs both the optically thick and optically thin. We investigate the dependence of the polarization of reflected radiation on the aperture angle of incident radiation. The aperture angle is determined by the radius of accretion disc and the height of the source above the disc. For optically thick accretion discs we show that, if the aperture angle is smaller 70 grad, then the wave electric field oscillations of reflected radiation are parallel to the accretion disc plane. For aperture angle greater than 70 grad the electric field oscillations are parallel to the plane "normal to accretion disc - the line of sight". The latter also holds for reflection from the optically thin accretion disc independent of the aperture angle value.