If the `file' option is chosen for the spectrum type, you must provide a text file of the spectrum in your current working directory. The first line of the text file must be the number of energies listed in the table. The remaining lines are the energy channel (in eV) and the flux in units of photons cm s erg or erg cm s erg (see next subsection). Note that XSTAR will appropriately renormalize the luminosity. Also, be aware that small numbers (less than 1.e-30, say), may result in undesired results owing to the limitations of many machines in the range of exponents. Again, remember that it is not necessary to use actual physical units in specifying the input spectrum (except to distinguish between photon and energy fluxes) since the entire spectrum is renormalized to conform to the luminosity specified.