Plane Polarization in Comptonization process: a Monte Carlo study

Kumar, N (2024) Plane Polarization in Comptonization process: a Monte Carlo study. In: Publications of the Astronomical Society of Australia .

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Abstract

High energies emissions observed in X-ray binaries (XRBs), active galactic nuclei (AGNs) are linearly polarized. The prominent mechanism for X-ray is the Comptonization process. We revisit the theory for polarization in Compton scattering with unpolarized electrons, and note that the (k�k�)-coordinate (in which, (k�k�) acts as a z-axis, here k and k� are incident and scattered photon momentum respectively) is more convenient to describe it. Interestingly, for a fixed scattering plane the degree of polarization PD after single scattering for random oriented low-energy unpolarized incident photons is �0.3. At the scattering angle θ = 0 orθ 0,25-, the modulation curve of k� exhibits the same PD and PA (angle of polarization) of k, and even the distribution of projection of electric vector of k� (k�e) on perpendicular plane to the k indicates same (so, an essential criteria for detector designing). We compute the polarization state in Comptonization process using Monte Carlo methods with considering a simple spherical corona. We obtain the PD of emergent photons as a function of =-angle (or alternatively, the disk inclination angle i) on a meridian plane (i.e., the laws of darkening, formulated by Chandrasekhar, 1946) after single scattering with unpolarized incident photons. To explore the energy dependency we consider a general spectral parameter set corresponding to hard and soft states of XRBs, we find that for average scattering no. a Nsca �1.1 the PD is independent of energy and PA � 90- (k�e is parallel to the disk plane), and for hNsci �5 the PD value is maximum for i = 45-. We also compare the results qualitatively with observation of IXPE for five sources. © The Author(s), 2024. Published by Cambridge University Press on behalf of the Astronomical Society of Australia.

Item Type:	Journal Article
Publication:	Publications of the Astronomical Society of Australia
Publisher:	Cambridge University Press
Additional Information:	The copyright for this article belongs to Author.
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	01 Mar 2024 10:55
Last Modified:	01 Mar 2024 10:55
URI:	https://eprints.iisc.ac.in/id/eprint/84189

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