The Radius of PSR J0740+6620 from NICER with NICER Background Estimates

Abstract We report a revised analysis for the radius, mass, and hot surface regions of massive millisecond pulsar PSR J0740+6620, studied previously with joint fits to NICER XMM-Newton data by Riley et al. (2021) Miller (2021). perform similar Bayesian estimation pulse-profile model parameters, except that instead fitting simultaneously data, we use best available background estimates constrain number photons detected from source. This approach eliminates any potential issues in cross-calibration between these two instruments, providing thus an independent check robustness analysis. The obtained neutron star parameter constraints are compatible already published results, slight dependence on how conservative imposed limits are. A tighter lower limit causes inferred radius increase, upper it decrease. also extend study emission geometry examine degree deviation antipodality regions. show there is significant offset antipodal spot configuration, mainly due non-half-cycle azimuthal separation emitting spots. angle antipode be above 25° 84% probability. seems exclude centered-dipolar magnetic field J0740+6620.