X-ray polarization signatures of Compton scattering in magnetic cataclysmic variables |
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| Authors: | A L McNamara Z Kuncic K Wu |
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| Institution: | School of Physics, University of Sydney, NSW 2006, Australia;Mullard Space Science Laboratory, University College London, Holmbury St Mary, Surrey RH5 6NT;Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong SAR |
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| Abstract: | Compton scattering within the accretion column of magnetic cataclysmic variables (mCVs) can induce a net polarization in the X-ray emission. We investigate this process using Monte Carlo simulations and find that significant polarization can arise as a result of the stratified flow structure in the shock-ionized column. We find that the degree of linear polarization can reach levels up to ～8 per cent for systems with high accretion rates and low white dwarf masses, when viewed at large inclination angles with respect to the accretion column axis. These levels are substantially higher than previously predicted estimates using an accretion column model with uniform density and temperature. We also find that for systems with a relatively low-mass white dwarf accreting at a high accretion rate, the polarization properties may be insensitive to the magnetic field, since most of the scattering occurs at the base of the accretion column where the density structure is determined mainly by bremsstrahlung cooling instead of cyclotron cooling. |
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| Keywords: | accretion accretion discs polarization scattering binaries: close white dwarfs |
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