optical flux ratio definition for source classification, we also had to convert the canonical ranges [@stocke1991] to our new system. The new ranges for different classes of objects are shown in Table \[fxfo\_classes\]. To calculate the new ranges of the X-ray to optical flux ratios, we assumed typical X-ray spectra for each class and calculated the shift in the X-ray flux due to the narrower energy band: a power law with a photon index of $\Gamma$=1-2.7 for AGN, a power law with a photon index of $\Gamma$=1-2 for BL Lac objects, a Raymond-Smith model with $kT=$2-7 keV, abundances of 0.1-0.6 and redshifts of $z=$0-1. For stars and supernova remnants we used Raymond-Smith models with energies of $kT$=0.5-2 keV, for X-ray binaries powerlaw models with photon index $\Gamma$=1-2. For galaxies, we adopted a somewhat ad hoc shift of 0.1-0.3 in the logarithm of the flux due to the different energy bands. This choice was motivated by examining different models for galaxies (warm and hot plasma mixture, powerlaw like emission from X-ray binaries, typical supernova remnant spectra, etc.).

For the shift in the optical flux (using R-band instead of the canonical V-band) we assumed typical values for each class.

The resulting ranges 