XSTAR warm absorber model

An analytic model for calculating warm absorber spectra within xspec is available. This has the advantage over the xstar table models that it avoids the intrinsic approximations associated with use of tables for absorption with variable abundances treated as multiplicative parameters, and the intrinsic clumsiness of the use of tables. It also allows the use of arbitrary spectral resolution, not limited by the internal xstar spectral resolution. To use it, go to the xstar page and follow the instructions there. Please send reports of bugs and problems to tim-at-xstar.gsfc.nasa.gov.