Six years of XMM-Newton observations of NGC 1313 X-1 and X-2

TL;DR

This study analyzes six years of XMM-Newton X-ray observations of NGC 1313 X-1 and X-2, revealing different spectral states and environmental metallicities, and interprets their accretion behaviors within super-Eddington and near Eddington frameworks.

Contribution

It provides a systematic spectral analysis over six years, modeling accretion states and environmental metallicities of two ultraluminous X-ray sources in NGC 1313.

Findings

NGC 1313 X-1 shows super-Eddington accretion behavior.

NGC 1313 X-2 exhibits near Eddington accretion characteristics.

The local environment of X-1 has solar metallicity, X-2 has sub-solar metallicity.

Abstract

We present a systematic analysis of the X-ray spectra of NGC 1313 X-1 and NGC 1313 X-2, using six years of XMM-Newton observations (17 observations). We fitted the continuum with a Comptonization model plus a multicolor blackbody disc, that describes the effects of an accretion disc plus an optically thick corona. We checked the consistency of this spectral model on the basis of the variability patterns of its spectral parameters. We found that the two sources show different spectral states. We tentatively interpret the observed behaviour of NGC 1313 X-1 within the framework of super-Eddington accretion and that of NGC 1313 X-2 within the framework of near Eddington accretion. We also attempted to determine the chemical abundances in the local environment of NGC 1313 X-1 and X-2, analyzing the RGS spectra of the longest observation available (122 ksec). The results appear to indicate solar metallicity for the local environment of NGC 1313 X-1 and sub-solar metallicity for NGC 1313 X-2.