A Hard Look at NS LMXBs with NuSTAR

Through NuSTAR we have been able to perform inner disk measurements that are unbiased by pile-up effects. From these measurements we are able to infer different properties about the neutron star itself, such as magnetic field estimates, the extent of the boundary layer, and constraints to the equation of state. NuSTAR has observed a number of neutron stars over range of Eddington ratios, which has allowed us to probe the extent of the inner disk over a range of mass accretion rates. There does not appear to be a clear trend between mass accretion rate and the location of the inner disk radius. This affirms the results of several previous studies that were complicated by pile-up effects. We compare the magnetic field strengths from reflection modeling methods to those seen for accreting millisecond X-ray pulsars (AMXPs). We find the magnetic field strengths to be consistent with AMXP’s over comparable Eddington ratios, though coherent pulsations have not yet been detected for some of these sources. Additionally, we explore possible implications for the equation of state of neutron stars.