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On the role of strong gravity in polarization from scattering of light in relativistic flows

J. Horak·V. Karas
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Abstract

We study linear polarization due to scattering of light on a cloudlet of particles, taking into account the radiation drag and the gravitational pull exerted on them by a central body. Effects of special and general relativity are included by connecting a model of Beloborodov (1998) for the local polarization of scattered light with Abramowicz, Ellis & Lanza (1990) formalism for the particle motion near an ultra-compact star. Compactness of the central body and its luminosity are two critical parameters of the model. We discuss the polarization magnitude of photons, which are Thomson-scattered into direct and higher-order images. Importance of the latter is only moderate under typical conditions, but they may give rise to distinct features, which we explore in terms of a toy model. The scattered signal exhibits variations of intensity and of polarization with mutual time-lags depending on the beaming/focusing effects and the light travel time.

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J. Horak, V. Karas. 2005-10-18. On the role of strong gravity in polarization from scattering of light in relativistic flows. https://doi.org/10.1111/j.1365-2966.2005.09748.x

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