Taking the beat of the UNSeEN openParThe Ultraluminous NS populatioN of ULXsclosePar

Due to their superEddington (L_Edd) Xray luminosity ULXs have long beenconsidered the ideal sample where to look for BHs of intermediate mass. Thediscovery of three ULXs showing pulsations unambiguously associated them to NSsexceeding 500 times their L_Edd. These discoveries challenge our understandingof accretion physics and pose a key question about the nature of the ULXs\\: arethey a population hosting both BHs and NSs, or is there a dominant new NSpopulation with extreme properties? This proposal involves a large fraction ofthe ULX community and is aimed at answering the above question by tripling thenumber of ULXs where sensitive searches for Xray pulsations and cyclotronfeatures can be carried out. We expect to detect 23 new PULXs, thus doubling the current sample. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]