The Radius of PSR J0740+6620 from NICER and XMM-Newton Data

By M. Miller, F. Lamb, A. Dittmann, S. Bogdanov, Z. Arzoumanian, K. Gendreau, S. Guillot, W. Ho, J. Lattimer, M. Loewenstein and 18 more. Astrophysical Journal Letters, 2021

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PSR J0740+6620 has a gravitational mass of 2.08 ± 0.07 M ⊙, which is the highest reliably determined mass of any neutron star. As a result, a measurement of its radius will provide unique insight into the properties of neutron star core matter at high densities. Here we report a radius measurement based on fits of rotating hot spot patterns to Neutron Star Interior Composition Explorer (NICER) and X-ray Multi-Mirror (XMM-Newton) X-ray observations. We find that the equatorial circumferential radius of PSR J0740+6620 is 13.7−1.5+2.6 km (68%). We apply our measurement, combined with the previous NICER mass and radius measurement of PSR J0030+0451, the masses of two other ∼2 M ⊙ pulsars, and the tidal deformability constraints from two gravitational wave events, to three different frameworks for equation-of-state modeling, and find consistent results at ∼1.5–5 times nuclear saturation density. For a given framework, when all measurements are included, the radius of a 1.4 M ⊙ neutron star is known to ±4% (68% credibility) and the radius of a 2.08 M ⊙ neutron star is known to ±5%. The full radius range that spans the ±1σ credible intervals of all the radius estimates in the three frameworks is 12.45 ± 0.65 km for a 1.4 M ⊙ neutron star and 12.35 ± 0.75 km for a 2.08 M ⊙ neutron star.

Subfields: Astronomy and Astrophysics, Geophysics, Oceanography

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Citations in the corpus

An Updated Mass–Radius Analysis of the 2017–2018 NICER Data Set of PSR J0030+0451 (2023, methodology): “So far the NICER collaboration has released results for two sources: PSR J0030 + 0451 ( Miller et al. 2019; Riley et al. 2019 ) and the high mass pulsar PSR J0740 + 6620 ( Miller et al. 2021; Riley et al. 2021; Salmi et al. 2022 ) .”
Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817 (2021, background): “indicated that NICER observations favor a mass–radius relation between Case 2 and Case 3 [108].”
On the Sound Speed in Neutron Stars (2022, methodology): “We impose the mass measurements of J0348+0432 (Antoniadis et al. 2013; M= 2.01± 0.04Me) and of J0740+6620 (Cromartie et al. 2019; Fonseca et al. 2021; M= 2.08± 0.07Me) by rejecting EOSs that have a maximum mass M M2.”
The Radius of the High-mass Pulsar PSR J0740+6620 with 3.6 yr of NICER Data (2024, background): “Re-sults for two sources have been released (Miller et al. 2019; Riley et al. 2019; Miller et al. 2021; Riley et al. 2021; Salmi et al. 2022, hereafter M21, R21, and S22; Vinciguerra et al. 2024), providing useful constraints for dense matter models (see, e.g., M21; Raaijmakers et al. 2021; Biswas…”
Observation of Gravitational Waves from the Coalescence of a 2.5–4.5 M ⊙ Compact Object and a Neutron Star (2024, methodology): “Both methods incorporate consistency with the observed heavy pulsars PSR J0740+6620 (Fonseca et al. 2021) and PSR J0348+0432 (Antoniadis et al. 2013) as priors on the EoS and enforce thermodynamic stability and causality.”
The NANOGrav 15 yr Data Set: Observations and Timing of 68 Millisecond Pulsars (2023, background): “Radio-derived neutron star mass constraints can be employed as priors in mass-to-radius measurements from X-ray light-curve modeling (e.g., Riley et al. 2021; Miller et al. 2021).”