090133

Ultraluminous X-ray sources (ULXs) are bright point-like sources likelyhosting accreting compact objects in binary systems. It is believed that manyULXs can host either neutron stars or stellar mass black holes accreting atsuper-Eddington rates although the relative number is not clear yet. Onlong-term timescales ULXs can be persistent or transient sources (i.e. fluxvariations of orders of magnitude) while their short-term variability ismarkedly different from source to source. Here we propose a 120 ks XMM-Newtonobservation of the galaxy NGC 7456 which hosts ULX-1 a source highly variableon timescales of a few ks. The main aim will be to characterize its extremeshort-term variability and spectral properties. At least other four transient ULXs are also present in the galaxy. [truncated! Please see actual data for full text]