Systematic spectral analysis of GX 339-4: influence of Galactic background and reflection models

TL;DR

This study systematically analyzes GX 339-4's X-ray spectra to understand how Galactic background and reflection models affect the interpretation of its spectral states.

Contribution

It introduces a precise Galactic background model and highlights the impact of reflection modeling choices on spectral parameter estimation.

Findings

Galactic background significantly influences spectral analysis at low fluxes.

Using Gaussian lines for reflection can falsely suggest high-temperature disks.

Incomplete reflection modeling leads to artifacts in spectral interpretation.

Abstract

Black hole X-ray binaries display large outbursts, during which their properties are strongly variable. We develop a systematic spectral analysis of the 3-40 keV RXTE/PCA data in order to study the evolution of these systems and apply it to GX 339-4. Using the low count rate observations, we provide a precise model of the Galactic background at GX 339-4's location and discuss its possible impact on the source spectral parameters. At higher fluxes, the use of a Gaussian line to model the reflection component can lead to the detection of a high-temperature disk, in particular in the high-hard state. We demonstrate that this component is an artifact arising from an incomplete modeling of the reflection spectrum.