Signal-to-noise ratio as a function of contrast (Δm) and separation for HiRISE without a coronagraph (red contour lines) and CRIRES+ standalone (black contour lines). The simulation is performed for a β Pictoris-like host star with a 1200 K planet and 2 h of integration time. The S/N is computed with a matched filtering approach (see Sect. 3.1) comparing the simulated spectra with the noiseless input planet spectrum. For this combination of parameters the S/N inward of 400 − 500 mas is dominated by the noise on the stellar halo. Outside of 400 − 500 mas it is limited by dark and read noise.