A NICER View of Neutron Stars

NICER, the Neutron Star Interior Composition Explorer, is a NASA X-ray telescope aboard the International Space Station designed for Pulse Profile Modeling (PPM) of rotation-powered Millisecond Pulsars (MSPs). PPM exploits relativistic effects on X-rays emitted from the hot magnetic polar caps on MSP surfaces. Leveraging NICER’s megasecond exposures, large effective collecting area, and high time and energy resolution, PPM has enabled precise measurements of these neutron stars’ properties, particularly mass and radius, yielding new insights into dense matter Equations of State (EoS).

In this talk, I will review the status of all published NICER targets using the open-source software package X-PSI (X-ray Pulse Simulation and Inference; github.com/xpsi-group/xpsi), namely PSR J0030+0451, PSR J0740+6620, PSR J0437−4715, and PSR J1231−1411, including any recent progress using updated datasets, as well as newer sources currently under investigation. I will discuss the implications of these findings for our understanding of ultradense matter and stellar magnetic fields, as well as ongoing efforts to enhance analysis methods in preparation for future X-ray telescope missions.