The Structure of the Relativistic Fe Line in GX 340+0 as Viewed with XRISM/Resolve, NICER, and NuSTAR

TL;DR

This study uses high-resolution X-ray observations from XRISM, NICER, and NuSTAR to analyze the iron emission line structure in the neutron star system GX 340+0 across different spectral states, revealing detailed features within the line complex.

Contribution

The paper provides the first high-resolution spectral analysis of GX 340+0's Fe line structure using XRISM, enhancing understanding of accretion disk reflection in neutron star systems.

Findings

Revealed detailed structure within the Fe K emission line complex.

Modeled the broad components of the reflection spectrum effectively.

Identified narrow emission features possibly due to ionized plasma.

Abstract

We present a 152 ks XRISM/Resolve observation of the persistently accreting Z source GX 340+0. Simultaneous observations also occurred with NuSTAR and NICER for 22.47 ks and 2.7 ks, respectively. The source covered the normal branch to the flaring branching during the observations. The data from all three missions were modeled concurrently for each spectral branch. The superior energy resolution of XRISM/Resolve reveals structure within the iron emission line complex regardless of spectral state. We model the reprocessed Fe K line with a reflection model tailored for thermal illumination of the accretion disk by a neutron star. The currently available model encompasses the broad components, but narrow emission features remain at the ~5% level. These remaining features may be described by the presence of an ionized plasma in the system as has been observed in the Z source Cygnus X-2, but subsequent updates to the reflection model code may be able to explain these features.