Illustration of the direct model for high-contrast long-slit spectroscopy given in Eq. (10). The data are modeled as the sum of two components: a stellar component and a companion component. Extracting the SED of the companion also requires the estimation of the on-axis PSF and the SED of the host star. The label “available via calibration” denotes components that may be self-calibrated by EXOSPECO directly from the science data (see Sect. 3.5 for details).