Multiple epoch analysis of NGC 7793 P9, an unusual ULX black hole.

NGC 7793 P9 is a little known ultra-luminous X-ray source (ULX) 3.40 Mpc away that has shown very intriguing behaviour. Hu et al. (2018) proposed that it is possibly a black hole X-ray binary due to its state change which could be connected to a change from sub- to super-Eddington accretion rate. Here we present a detailed spectral analysis of archival and new XMM-Newton and NuSTAR data, describing them with a two-component accretion disk model. While most data follow a canonical L \(\propto\) T⁴ relation, one observation is a stark outlier, with a much higher inner disk temperature than expected. This might indicate a significant change in accretion geometry as a function of flux. However, other observations at similar luminosities do not show this behaviour. Additionally, we find that all observations, below and above the fiducial Eddington limit of 10³⁹ erg/s can be described with the same two-component disk model and no further state changes are evident in our data. For this reason, we support a scenario in which the use of a two-component disk model can explain all P9’s states and where an accretion geometry change by cause of flux’s variability could be present.