Prism spectrum of the region to the north-east of GN-z11, from the February 2023 MSA observation. Top panel: signal-to-noise 2D prism spectrum of GN-z11. The spectrum has been obtained by using only the exposures in which GN-z11 is in the upper and lower shutters (hence discarding the exposure with GN-z11 in the central shutter) as to avoid self-subtraction of the extended signal. Bottom panel: one-dimensional spectrum extracted from the region delimited by the two dashed horizontal lines, at about 0.45″ from GN-z11 in the NE direction, illustrating the tentative detection (3.7σ integrated) of a feature at 1.903 μm. The red vertical line indicates the location of HeIIλ1640 expected at the redshift of GN-z11, z = 10.603 (which is indistinguishable from the redshift of 10.600 inferred for the grating spectrum).