# Suzaku spectroscopy of the neutron star transient 4U 1608-52 during its outburst decay

## TL;DR

This study uses Suzaku X-ray data to analyze the spectral states of the neutron star binary 4U 1608-52 during outburst decay, confirming a three-component model's effectiveness across different states.

## Contribution

It demonstrates that a three-component spectral model accurately describes the broad-band X-ray spectra of 4U 1608-52 across all classical states, supporting similar state evolution in neutron star and black hole binaries.

## Key findings

- The model fits data from soft to hard states successfully.
- In the soft state, the neutron star surface dominates seed photons.
- In the hard state, either the disc or neutron star surface can be the seed photon source.

## Abstract

We test the proposed 3-component spectral model for neutron star low mass X-ray binaries using broad-band X-ray data. We have analysed 4 X-ray spectra (0.8-30 keV) obtained with Suzaku during the 2010 outburst of 4U 1608-52, which have allowed us to perform a comprehensive spectral study covering all the classical spectral states. We use a thermally Comptonized continuum component to account for the hard emission, as well as two thermal components to constrain the accretion disc and neutron star surface contributions. We find that the proposed combination of multicolor disc, single-temperature black body and Comptonization components successfully reproduces the data from soft to hard states. In the soft state, our study supports the neutron star surface (or boundary layer) as the dominant source for the Comptonization seed photons yielding the observed weak hard emission, while in the hard state both solutions, either the disc or the neutron star surface, are equally favoured. The obtained spectral parameters as well as the spectral/timing correlations are comparable to those observed in accreting black holes, which support the idea that black hole and neutron star low mass X-ray binaries undergo a similar state evolution during their accretion episodes.