The NICER-NuSTAR View of accretion disks in NS LMXBs

Relativistic disk lines in neutron star low-mass X-ray binaries provide a valuable tool to determine the stellar magnetic field strength, the extent of a boundary layer, and even to place a limit on the radius of the compact object itself. Using NuSTAR, we have recently been able to obtain measurements of the inner disk around neutron stars that are unbiased by pile-up effects. Now, NICER affords the opportunity to search for low-energy relativistic lines down to 0.25 keV using detectors that are also free of distortions at high flux levels. The combined bandpass and sensitivity of NuSTAR and NICER open a new opportunity to capture multiple emission features, and to utilize them to measure and map out different observables within the disk (e.g., temperature, ionization, elemental abundance, etc.).