The orbit and spectra of the brightest accreting pulsar: NGC 5907 ULX-1

NGC 5907 ULX1 is the most luminous of the 3 ULXs known to be accreting pulsars.At 17.1 Mpc, its Xray isotropic luminosity peaks at 1e41 erg/s, 500 times theEddington limit for a NS. Understanding the physics of this extreme object, fora long time prototypical of IMBHs, which defeats simple theoreticalexplanations, is interesting per se and essential for population studies andsearches for pulsation in other ULXs. The most effective strategy is torepeatedly observe it with XMM and NuSTAR with a carefully devised schedule.Their synergy will provide us also with orbital and spinphaseresolvedbroadband Xray spectroscopy, essential for a better understanding of thisobject, in the context of other extreme ULXs. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]