Complex Ionization and Velocity Structures in GX 340+0 X-ray Binary Revealed by XRISM

TL;DR

This paper presents the first high-resolution XRISM spectrum of GX 340+0, revealing complex ionization, velocity structures, and a relativistic reflection feature, advancing understanding of neutron star low-mass X-ray binaries.

Contribution

It provides detailed modeling of emission and absorption features, uncovering multi-ionization, multi-velocity structures, and a disk wind in GX 340+0, using state-of-the-art spectral synthesis and reflection models.

Findings

Detection of a 2735 km/s accretion disk wind with absorption and emission features.

Identification of complex Fe XXV Heα line profiles with multiple components.

Observation of a relativistic reflection feature modeled with relxillNS.

Abstract

We present the first high-resolution XRISM spectrum of the neutron star low-mass X-ray binary GX 340+0, revealing unprecedented detail in its emission and absorption features. The spectrum reveals a rich and complex Fe XXV He$\alpha$ line profile and a P-Cygni profile from Ca XX. We use the state-of-the-art spectral synthesis code Cloudy to model the emission and absorption features in detail. Our analysis reveals multi-ionization and multi-velocity structures, where the combination of broad ($\sim$ 800 km/s) and narrow ($\sim$ 360 km/s) line components, along with rest-frame and blueshifted emission and absorption lines, accounts for the observed line profile complexity. We identify a modest $\sim$ 2735 km/s accretion disk wind exhibiting both absorption and emission features. We also detect a relativistic reflection feature in the spectrum, which we model using relxillNS - specifically designed to characterize X-ray reprocessing in accretion disks around neutron stars. Furthermore, we examine the detailed physics of the Fe XXV He$\alpha$ complex, focusing on the forbidden-to-resonance line ratio under the influence of continuum pumping and optical depth effects.