Cloudy in the microcalorimeter era: improved energies for Si and S K$\alpha$ fluorescence lines

TL;DR

This paper enhances the spectral simulation accuracy for upcoming X-ray missions by updating fluorescence energies in Cloudy, leading to better modeling of astrophysical spectra, particularly for Si and S lines.

Contribution

The authors update Cloudy's fluorescence energy table with laboratory measurements, significantly improving spectral modeling accuracy for Si and S Kα lines.

Findings

Improved spectral fits for Vela X-1 using updated energies

Remarkable agreement with laboratory measurements

Significant enhancement over previous Cloudy version

Abstract

The upcoming X-ray missions based on the microcalorimeter technology require exquisite precision in spectral simulation codes in order to match the unprecedented spectral resolution. In this work, we improve the fluorescence K$\alpha$ energies for Si II-XI and S II-XIII in the code Cloudy. In particular, we provide here a patch to update the Cloudy fluorescence energy table, originally based on Kaastra & Mewe (1993), with the laboratory energies measured by Hell et al. (2016). The new Cloudy simulations were used to model the Chandra/HETG spectra of the High Mass X-ray Binary Vela X-1 previously presented in Amato et al. (2021), showing a remarkable agreement and a dramatic improvement with respect to the current release version of Cloudy (C17.02).