Insight in the Emission Mechanisms of the Brightest ULX in the Cartwheel

The compact X-ray source N10 detected in the Cartwheel ring is one of the brightest ULXs in the sky. I will present results on the variability of this source, and its spectrum. I will discuss the inferred parameters in the context of the current theoretical models. Due to the low statistics, we cannot clinch down the argument on the nature of N10. Nonetheless, I will show that the available information allow us to constrain the parameter space for black hole accretion.