Shedding light to the highly variable Ultraluminous X-ray source NGC 7456

ULXs are very luminous, point-like sources, likely hosting accretingcompact objects in binary systems. It is believed that many ULXscan host either NSs or stellar mass BHs accreting at super-Eddingtonrates, although the relative number is not clear yet. On long-termtimescales ULXs can be persistent or transient sources (i.e. with fluxvariations of orders of magnitude), while their short-term variability ismarkedly different from source to source. We propose a 130ks XMM- Newtonobservation of the galaxy NGC 7456, which hosts ULX-1, a source highlyvariable on timescales of a few ks. The main aim is to characterize itsextreme short-term variability and spectral properties. This proposalwas accepted in C- priority in AO19, but the observation has not yetobtained at the AO20 deadline.