New realistic models for the X-ray polarization of neutron stars

X-ray polarimetry is quickly becoming a reality: the ISRO POLIX and the NASA IXPE are planned to launch in 2021, while eXTP, the Chinese X-ray observatory, has recently entered its phase B and will be in orbit by the end of 2025. The emission from accreting neutron stars, as well as from the highly magnetized neutron stars called magnetars, is dominated by X-rays, and therefore these objects will be among the main targets for the upcoming polarimeters. Modeling of the X-ray emission from these objects is complicated by the presence of strong magnetic and gravitational fields, and of rapid bulk motions of the emitting plasma; however, observations of the polarized emission can provide insight on the accretion geometry and on the structure and strength of the magnetic field. I will present new models for accreting X-ray pulsars and magnetars, based on our current understanding of the emission mechanisms, that agree with current spectroscopic observation and that predict the phase-resolved polarization degree as a function of energy and geometry of the source.