Added the effect of photoionization and heating by line photons generated elsewhere in the cloud. These are photons which have already escaped the local region close to the point of emission.
Changed the step size computation algorithm in order to account for the process of emission. That is, the step size is now is based on the length scale for significant change of both absorption and emission.
Fixed several errors in the atomic database, notably affecting N-like ions. These affect some of the density sensitive lines in low ionization models.
Update to this manual, in the chapter in the Physics of xstar, describing in more detail the radiation transfer algorithm.