paper

The Radius of the High-mass Pulsar PSR J0740+6620 with 3.6 yr of NICER Data

arXiv:2406.14466 · doi:10.3847/1538-4357/ad5f1f

Abstract

We report an updated analysis of the radius, mass, and heated surface regions of the massive pulsar PSR J0740+6620 using Neutron Star Interior Composition Explorer (NICER) data from 2018 September 21 to 2022 April 21, a substantial increase in data set size compared to previous analyses. Using a tight mass prior from radio timing measurements and jointly modeling the new NICER data with XMM-Newton data, the inferred equatorial radius and gravitational mass are km and respectively, each reported as the posterior credible interval bounded by the and quantiles, with an estimated systematic error km. This result was obtained using the best computationally feasible sampler settings providing a strong radius lower limit but a slightly more uncertain radius upper limit. The inferred radius interval is also close to the km obtained by Dittmann et al., when they require the radius to be less than km as we do. The results continue to disfavor very soft equations of state for dense matter, with km for this high-mass pulsar excluded at the probability. The results do not depend significantly on the assumed cross-calibration uncertainty between NICER and XMM-Newton. Using simulated data that resemble the actual observations, we also show that our pipeline is capable of recovering parameters for the inferred models reported in this paper.

arXiv comment17 pages, 9 figures (2 of which are figure sets), 2 tables, published in ApJ

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