Checking Potassium origin of new emission line at 3.5 keV with K XIX line complex at 3.7 keV

TL;DR

This paper investigates whether the unexplained 3.5 keV emission line in galaxy observations originates from Potassium lines, proposing future X-ray spectrometry of the K XIX complex at 3.7 keV for confirmation.

Contribution

It introduces a method using the K XIX line complex at 3.7 keV to test the Potassium origin of the 3.5 keV line with upcoming X-ray instruments.

Findings

The 3.7/3.5 keV ratio uncertainty can be reduced with better modeling.

Future X-ray spectrometers can directly test Potassium origin.

Current data cannot conclusively determine the line's origin.

Abstract

Whether the new line at ~3.5 keV, recently detected in different samples of galaxy clusters, Andromeda galaxy and central part of our Galaxy, is due to Potassium emission lines, is now unclear. By using the latest astrophysical atomic emission line database AtomDB v. 3.0.2, we show that the most prospective method to directly check its Potassium origin will be the study of K XIX emission line complex at ~3.7 keV with future X-ray imaging spectrometers such as Soft X-ray spectometer on-board Astro-H mission or microcalorimeter on-board Micro-X sounding rocket experiment. To further reduce the remaining (factor ~3-5) uncertainty of the 3.7/3.5 keV ratio one should perform more precise modeling including removal of significant spatial inhomogeneities, detailed treatment of background components, and further extension of the modeled energy range.