BROADBAND OBSERVATIONS OF NEW ULXS: IC5052 ULX AND ESO501-023 ULX

The ultraluminous Xray source population is now broadly expected to bedominated by superEddington accretors, thanks to the broadband spectroscopyprovided by NuSTAR and XMMNewton in combination, and the detection of Xraypulsations from a growing subset of ULXs (unambiguously confirming them assuperEddington neutron stars). IC 5052 ULX and ESO 501023 ULX are extreme ULXs(LX;peak > 1040 erg so???1) that have received very little observationalattention to date. Here, we propose coordinated 100+50 ks NuSTAR+XMMNewtonobservations of these sources in order to constrain their broadband spectra andsearch for pulsations. These observations will provide the first robustconstraints on the nature of these two extreme binary systems. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]