BUCCIANTINI, Niccolo'Niccolo'BUCCIANTINIDi Lalla, N.N.Di LallaRomani, R. W. R.R. W. R.RomaniSilvestri, S.S.SilvestriNegro, M.M.NegroBaldini, L.L.BaldiniTennant, A. F.A. F.TennantManfreda, A.A.Manfreda2025-05-152025-05-1520230004-6361http://hdl.handle.net/20.500.12386/37129X-ray polarimetry, based on Gas Pixel Detectors (GPDs), have reached a high level of maturity with the Imaging X-ray Polarimeter Explorer (IXPE) leading to the first ever spatially resolved polarimetric measures. However, being this a new technique, a few unexpected effect have emerged during in flight operations. In particular it was almost immediately found that on-board unpolarized calibration sources were showing radially polarized halos. The origin of this features was recognized in a correlation between the error in reconstructing the absorption point of the X-ray photon and the direction of its electric field vector. Here we present and discuss in detail this effect, showing that it is possible to provide a simple and robust mathematical formalism to handle it. We further show its role and relevance for the recent IXPE measures, and for the use of GPD-based techniques in general, and illustrate how to model it in the study of extended sources.STAMPAenArticle10.1051/0004-6361/2022457442-s2.0-85153367698https://www.aanda.org/articles/aa/full_html/2023/04/aa45744-22/aa45744-22.htmlhttp://arxiv.org/abs/2302.00346v2FIS/05 - ASTRONOMIA E ASTROFISICA