The Radius of the High Mass Pulsar PSR J0740+6620 With 3.6 Years of NICER Data
Abstract
We report an updated analysis of the radius, mass, and heated surface regions of the massive pulsar PSR J0740+6620 using 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 XMMNewton data, the inferred equatorial radius and gravitational mass are $12.49_{0.88}^{+1.28}$ km and $2.073_{0.069}^{+0.069}$ $M_\odot$ respectively, each reported as the posterior credible interval bounded by the $16\,\%$ and $84\,\%$ quantiles, with an estimated systematic error $\lesssim 0.1$ 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 $R=12.76_{1.02}^{+1.49}$ km obtained by Dittmann et al. 2024, when they require the radius to be less than $16$ km as we do. The results continue to disfavor very soft equations of state for dense matter, with $R<11.15$ km for this high mass pulsar excluded at the $95\,\%$ probability. The results do not depend significantly on the assumed crosscalibration uncertainty between NICER and XMMNewton. 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.
 Publication:

arXiv eprints
 Pub Date:
 June 2024
 DOI:
 10.48550/arXiv.2406.14466
 arXiv:
 arXiv:2406.14466
 Bibcode:
 2024arXiv240614466S
 Keywords:

 Astrophysics  High Energy Astrophysical Phenomena;
 Nuclear Theory
 EPrint:
 17 pages, 9 figures (2 of which are figure sets), 2 tables, accepted for publication in ApJ