Argon X-ray absorption in the local interstellar medium

We present the first comprehensive analysis of the argon K-edge absorption region (3.1–4.2 Å) 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.