A NICER View of the Massive Pulsar PSR J0740+6620 Informed by Radio Timing and XMM-Newton Spectroscopy

By T. E. Riley, A. Watts, P. Ray, S. Bogdanov, S. Guillot, S. Morsink, A. Bilous, Z. Arzoumanian, Devarshi Choudhury, Julia Deneva and 20 more. Astrophysical Journal Letters, 2021

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We report on Bayesian estimation of the radius, mass, and hot surface regions of the massive millisecond pulsar PSR J0740+6620, conditional on pulse-profile modeling of Neutron Star Interior Composition Explorer X-ray Timing Instrument event data. We condition on informative pulsar mass, distance, and orbital inclination priors derived from the joint North American Nanohertz Observatory for Gravitational Waves and Canadian Hydrogen Intensity Mapping Experiment/Pulsar wideband radio timing measurements of Fonseca et al. We use XMM-Newton European Photon Imaging Camera spectroscopic event data to inform our X-ray likelihood function. The prior support of the pulsar radius is truncated at 16 km to ensure coverage of current dense matter models. We assume conservative priors on instrument calibration uncertainty. We constrain the equatorial radius and mass of PSR J0740+6620 to be 12.39−0.98+1.30 km and 2.072−0.066+0.067 M ⊙ respectively, each reported as the posterior credible interval bounded by the 16% and 84% quantiles, conditional on surface hot regions that are non-overlapping spherical caps of fully ionized hydrogen atmosphere with uniform effective temperature; a posteriori, the temperature is log10(T[K])=5.99−0.06+0.05 for each hot region. All software for the X-ray modeling framework is open-source and all data, model, and sample information is publicly available, including analysis notebooks and model modules in the Python language. Our marginal likelihood function of mass and equatorial radius is proportional to the marginal joint posterior density of those parameters (within the prior support) and can thus be computed from the posterior samples.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/2f2cdb2025a329b3b6620b675755fe631aaf4bd4

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Citations in the corpus

On the Sound Speed in Neutron Stars (2022, methodology): “In addition, we impose the radius measurements by NICER of J0740+6620 (Miller et al. 2021; Riley et al. 2021) and of J0030+0451 (Riley et al. 2019; Miller et al. 2019) by rejecting EOSs with R< 10.75 km at M= 2.0Me and R< 10.8 km at M= 1.1Me, respectively (see Figure 6 in the Appendix).”
An Updated Mass–Radius Analysis of the 2017–2018 NICER Data Set of PSR J0030+0451 (2023, methodology): “As in Salmi et al. ( 2022 ) , in this work we adopt the compressed effective area prior ( see Section 4.2 of Riley et al. 2021 ) .”
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…”
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).”
Observation of Gravitational Waves from the Coalescence of a 2.5–4.5 M ⊙ Compact Object and a Neutron Star (2024, methodology): “…(Section 7), we repeat these analyses using GP-EoS constraints additionally conditioned on NICER observations (Legred et al. 2021, 2022) of J0030+0451 (Miller et al. 2019; Riley et al. 2019; Vinciguerra et al. 2024) and J0740+6620 (Miller et al. 2021; Riley et al. 2021; Salmi et al. 2022, 2023).”