The Burst Spectra of EXO 0748-676 during a Long 2003 XMM-Newton Observation

TL;DR

This study analyzes a long XMM-Newton observation of neutron star EXO 0748-676 to investigate the presence of gravitationally redshifted iron absorption lines, finding that spectral features vary with photospheric conditions.

Contribution

It provides a detailed analysis of burst spectra over a 600 ks observation, highlighting the variability of absorption features and their dependence on photospheric conditions.

Findings

Previous iron absorption lines were not detected in new data.

Spectral features are sensitive to changes in photospheric conditions.

The variability suggests dynamic photospheric environments.

Abstract

Gravitationally redshifted absorption lines from highly ionized iron have been previously identified in the burst spectra of the neutron star in EXO 0748-676. To repeat this detection we obtained a long, nearly 600 ks observation of the source with XMM-Newton in 2003. The spectral features seen in the burst spectra from the initial data are not reproduced in the burst spectra from this new data. In this paper we present the spectra from the 2003 observations and discuss the sensitivity of the absorption structure to changes in the photospheric conditions.