Argon X-ray absorption in the local interstellar medium

Abstract

We present the first comprehensive analysis of the argon K-edge absorption region (3.1-4.2 & Aring;) using high-resolution HETGS Chandra spectra of 33 low-mass X-ray binaries. Utilizing R-matrix theory, we computed new K photoabsorption cross sections for Ar I-Ar XVI species. For each X-ray source, we estimated column densities for the Ar I, Ar II, Ar III, Ar XVI, Ar XVII, and Ar XVIII ions, which trace the neutral, warm, and hot components of the gaseous Galactic interstellar medium. We examined their distribution as a function of Galactic latitude, longitude, and distances to the sources. However, no significant correlations were discerned among distances, Galactic latitude, or longitude. Future X-ray observatories will allow us to benchmark the atomic data as the main resonance lines will be resolved.