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

M. C. Miller, F. K. Lamb, A. J. Dittmann, S. Bogdanov, Z. Arzoumanian, K. C. Gendreau, S. Guillot, W. C.G. Ho, J. M. Lattimer, M. Loewenstein, S. M. Morsink, P. S. Ray, M. T. Wolff, C. L. Baker, T. Cazeau, S. Manthripragada, C. B. Markwardt, T. Okajima, S. Pollard, I. CognardH. T. Cromartie, E. Fonseca, L. Guillemot, M. Kerr, A. Parthasarathy, T. T. Pennucci, S. Ransom, I. Stairs

Research output: Contribution to journalArticlepeer-review


PSR J0740+6620 has a gravitational mass of 2.08 ± 0.07 M o˙, 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 o˙ 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 o˙ neutron star is known to ±4% (68% credibility) and the radius of a 2.08 M o˙ 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 o˙ neutron star and 12.35 ± 0.75 km for a 2.08 M o˙ neutron star.

Original languageEnglish (US)
Article numberL28
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Sep 10 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'The Radius of PSR J0740+6620 from NICER and XMM-Newton Data'. Together they form a unique fingerprint.

Cite this