Argon X-ray absorption in the local ISM

TL;DR

This study analyzes argon K-edge absorption in the interstellar medium using high-resolution X-ray spectra, providing new atomic data and ion column densities across multiple sources to understand Galactic gas distribution.

Contribution

It introduces new R-matrix computed argon photoabsorption cross-sections and applies them to estimate ion column densities in the ISM from X-ray observations.

Findings

No significant correlation between argon ion distributions and Galactic coordinates.

New atomic data for argon K-edge absorption are provided.

Ion column densities trace different phases of the Galactic ISM.

Abstract

We present the first comprehensive analysis of the argon K-edge absorption region (3.1-4.2 \AA) using high-resolution HETGS {\it Chandra} spectra of 33 low-mas X-ray binaries. Utilizing R-matrix theory, we computed new K photoabsorption cross-sections for {\rm Ar}~{\sc i}--{\rm Ar}~{\sc xvi} species. For each X-ray source, we estimated column densities for the {\rm Ar}~{\sc i}, {\rm Ar}~{\sc ii}, {\rm Ar}~{\sc iii}, {\rm Ar}~{\sc xvi}, {\rm Ar}~{\sc xvii} and {\rm Ar}~{\sc 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.