High-Resolution Study of X-ray Absorption by the Interstellar Medium

A proper understanding of the absorption of X-rays by the interstellar medium is important for the spectral modeling of X-ray sources. The XSPEC model tbabs takes into account improved abundances, new cross sections, and the influence of grains. We describe recent improvements to tbabs, including the addition of fine structure in the absorption edges of Fe-L, O, and Ne, which allow tbabs to be used with gratings instruments such as the Chandra HETGS and LETGS and the RGS on XMM-Newton.