Unlocking the nature of ultraluminous X-ray sources using their X-ray spectra

TL;DR

This study analyzes high-quality X-ray spectra of ultraluminous X-ray sources to understand their physical nature, suggesting they involve super-Eddington accretion onto stellar-mass black holes.

Contribution

It combines phenomenological and physically-motivated spectral models to investigate the accretion processes in ULXs, providing insights into their extreme physical conditions.

Findings

Spectral analysis indicates super-Eddington accretion.

Physically-motivated models support stellar-mass black hole origin.

High-quality data enables detailed spectral characterization.

Abstract

We explore the nature of ultraluminous X-ray sources through detailed investigations of their spectral shape using some of the highest quality data available in the XMM-Newton public archives. Phenomenological models allow us to characterise their spectra, while more 'physically-motivated' models enable us to explore the physical processes underlying these characteristics. These physical models imply the presence of extreme (probably super-Eddington) accretion on to stellar mass black holes.