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arXiv · 1208.3314

X-ray polarimetry as a new tool to discriminate reflection from absorption scenarios -- Predictions for MCG-6-30-15

F. Marin·R. W. Goosmann·M. Dovciak·F. Muleri·D. Porquet·N. Grosso·V. Karas·G. Matt
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Abstract

We present modelling of X-ray polarisation spectra emerging from the two competing scenarios that are proposed to explain the broad Fe Kα line in the Seyfert 1 galaxy MCG-6-30-15. The polarisation signature of complex absorption is studied for a partial covering scenario using a clumpy wind and compared to a reflection model based on the lamp-post geometry. The shape of the polarisation percentage and angle as a function of photon energy are found to be distinctly different between the reflection and the absorption case. Relativistic reflection produces significantly stronger polarisation in the 1-10 keV energy band than absorption. The spectrum of the polarisation angle adds additional constraints: in the absorption case it shows a constant shape, whereas the relativistic reflection scenario typically leads to a smooth rotation of the polarisation angle with photon energy. Based on this work, we conclude that a soft X-ray polarimeter on-board a small X-ray satellite may already discriminate between the absorption and the reflection scenario. A promising opportunity may arise with the X-ray Imaging Polarimetry Explorer (XIPE) mission, which has been proposed to ESA in response to a small-size (S-class) mission call due for launch in 2017.

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F. Marin, R. W. Goosmann, M. Dovciak, F. Muleri, D. Porquet, N. Grosso, V. Karas, G. Matt. 2012-08-16. X-ray polarimetry as a new tool to discriminate reflection from absorption scenarios -- Predictions for MCG-6-30-15. https://doi.org/10.1111/j.1745-3933.2012.01335.x

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