The exposure images, products from running mos_spectra, mos-back, or pn_spectra, pn-back, and, eventually comb, following the particular nomenclature used in the esas package, eg.: mos1S002-obj-im-350-800.fits for a MOS1 image in that spectral range, or comb-obj-im-350-800.fits if the output from comb is to be used.