Shedding light onto the highly variable Ultraluminous X-ray source NGC7456

Ultraluminous X-ray sources (ULXs) are bright, point-like sources,likely hosting accreting compact objects in binary systems. It isbelieved that many ULXs can host either neutron stars or stellar massblack holes accreting at super-Eddington rates, although the relativenumber is not clear yet. On long-term timescales ULXs can be persistentor transient sources (i.e. flux variations of orders of magnitude),while their short-term variability is markedly different from source tosource. Here we propose a 120 ks XMM-Newton observation of the galaxyNGC 7456, which hosts ULX-1, a source highly variable on timescales ofa few ks. The main aim will be to characterize its extreme short-termvariability and spectral properties. At least other four transient ULXsare also present in the galaxy.