IXPE and XMM-Newton Observations of the Soft Gamma Repeater SGR 1806-20 - Turolla R.; Taverna R.; Israel G.L.; Muleri F.; Zane S.; Bachetti M.; Heyl J.; Di Marco A.; Gau E.; Krawczynski H.; Ng M.; Possenti A.; et al. (Institute of Physics, 2025)