AtomDB AtomDB is an atomic database useful for X-ray plasma spectral modeling.
simx simx simulates a photon-counting detector's response to an input source; it currently can simulate observations from the X-ray Surveyor, Athena, Hitomi, and microX. It is designed to be a 'approximation' tool to estimate issues such as source confusion, background effects, pileup, and other similar issues
xscat The purpose of `xscat' is to calculate the X-ray scattering cross section of a population of dust grains as a function of energy, given a specific dust grain position and an extraction region.
acx ACX is an approximate model of charge exchange emission in an astrophysical context, usable within XSPEC.