HIDs of GX 340+0 in 150 s time bin. Top panel: HID of GX 340+0 from the NICER data archive (grey points). The coloured points represent the five NICER observations performed during the IXPE one and also reported in Table 1 and Fig. 1-top as shaded coloured regions in the IXPE light curve. Bottom panel: HID of GX 340+0 from the NuSTAR archival data (grey points). The olive green points represent the NuSTAR observation selected to perform the spectral and spectropolarimetric analysis.