088355

Within the framework of the AO17 UNSEEN XMM Large Program comma we discovered a new 2.8-s Pulsating ULX hosted in a massive binary system openParMc>8MsunclosePar in M51 with an orbital period of 2 days and a super-orbital modulation of about 38 days. Being a persistent source openParunlike all the other known PULXsclosePar it is very well suited for deeper studies. The present proposal is two-foldeddoublePoint improving our understanding of the accretion phenomena onto Neutron Stars openParNSsclosePar at extreme rates and extending our knowledge of M51 ULX-7. The requested pointings comma together with the archival datasets comma will allow us to measure crucial orbital parameters in order to prove whether PULXs have indeed super-Eddington luminosities or are mainly beamed- emitting NSs comma a long standing problem in the field.