A NICER View of PSR J0030+0451 Updated Constraints from 6 yr of NICER Observations

Pulse-profile modeling of rotation-powered millisecond pulsars targeted by NICER has enabled mass–radius constraints of several neutron star sources, with implications for the dense-matter equation of state. For the bright isolated pulsar PSR J0030+0451, the inferred mass and radius were previously found to depend strongly on the assumed hot-spot model. These hot-spot models yielded different mass–radius constraints, with the statistically preferred model exhibiting some mild tension with results inferred for PSR J0437−4715, PSR J0614−3329, and GW170817. We present an updated pulse-profile analysis of PSR J0030+0451 using new NICER observations obtained between 2017 July to 2023 January, increasing the number of X-ray counts by about 50% compared to previous analyses. We jointly analyze the NICER data with archival XMM-Newton observations to better constrain the source spectrum and background. The new analysis, using more conservative nested-sampling settings together with the new NICER observations, significantly reduces the discrepancy between the hot-spot models. The inferred mass and radius are (Formula presented) M = 1.43^+0.20_−0.17 M_⊙ and R_eq= 12.68^+1.31_−1.04 km (68% credible intervals), reducing the tension with the results from other sources. In addition, the inferred hot-spot configurations suggest the presence of intraspot temperature gradients.