Testing reflection features in 4U 1705-44 with XMM-Newton, BeppoSAX and RXTE in the hard and soft state

TL;DR

This study analyzes the reflection features of the atoll source 4U 1705-44 across hard and soft states using data from XMM-Newton, BeppoSAX, and RXTE, revealing state-dependent spectral differences.

Contribution

It provides a self-consistent broadband spectral analysis of 4U 1705-44 in different states using multiple observatories and reflection models, highlighting changes in the accretion disk radius.

Findings

Reflection models fit the spectra well in both states.

Inner disk radius slightly recedes in the hard state.

Spectral parameters differ between states.

Abstract

We use data of the bright atoll source 4U 1705-44 taken with XMM-Newton, BeppoSAX and RXTE both in the hard and in the soft state to perform a self-consistent study of the reflection component in this source. Although the data from these X-ray observatories are not simultaneous, the spectral decomposition is shown to be consistent among the different observations, when the source flux is similar. We therefore select observations performed at similar flux levels in the hard and soft state in order to study the spectral shape in these two states in a broad band (0.1-200 keV) energy range, with good energy resolution, and using self-consistent reflection models. These reflection models provide a good fit for the X-ray spectrum both in the hard and in the soft state in the whole spectral range. We discuss the differences in the main spectral parameters we find in the hard and the soft state, respectively, providing evidence that the inner radius of the optically thick disk slightly recedes in the hard state.