086276

We propose a broadband observation of the transient ULX comma NGC 925 ULX-3 comma for 40ks with XMM-Newton quasi-simultaneous with a 100ks observation with NuSTAR. This source exhibits extreme levels of long-term variability of over a factor of 36 comma a feature also seen in several ULXs identified as neutron stars to date and linked to different possible mechanisms that are not well understood. We plan to trigger this observation when the source exceeds a flux of 6x10elev and #8722 13 ergs-s-cm2 comma determined from an existing Swift monitoring campaign comma allowing us to constrain its high-flux broadband spectrum. Coupled with this monitoring and a complementary proposal at a low flux comma we will be able to build an understanding of the geometry and physical processes in play in this extreme accreting system.