092317

Modelling of the waveform of the X-ray pulsations of accreting ms pulsars (AMSP)is one of the most promising ways to constrain the equation of state of neutronstars. However it requires an extremely high number of counts to break thedegeneracy between the many parameters that shape the X-ray pulse profiles. Thepolarimetric information granted by the forthcoming IXPE mission will measurethe geometry of the hot spots independently easing the requirement. We proposea 120 ks XMM-NuSTAR ToO observation of the next outburst of an AMSP to measurethe pulsar ephemeris and fold simultaneous IXPE data model the broadbandspectrum and derive a high statistics energy-resolved pulse profile. Theproposed observation will measure the mass and the radius with an accuracy of a few per cent. [truncated! Please see actual data for full text]