087093

Multi-epoch broadband spectroscopy of the ultraluminous X-ray source openParULXclosePar NGC1313 X-1 has revealed unusual spectral variability. When fit with accretion disk models comma the data show two distinct groups in the L-T plane comma each of which exhibits its own positive L-T correlation. Understanding this behaviour is likely key to understanding the structure of super-Eddington accretion flows. Holmberg IX X-1 also shows some evidence for this behaviour comma but there is currently only one broadband observation in the high-flux regime comma meaning this cannot yet be firmly established. This proposal aims to take a series of 4 XMM+NuSTAR observations openPareach 25+50ksclosePar of Holmberg IX X-1 in its high-flux state in order to determine whether it does show the same unusual behaviour as NGC1313 X-1.