{"paper":{"title":"The Radius of PSR J0740+6620 from NICER and XMM-Newton Data","license":"http://arxiv.org/licenses/nonexclusive-distrib/1.0/","headline":"The highest-mass neutron star with a reliable radius measurement has an equatorial circumference of 13.7 km.","cross_cats":["gr-qc","nucl-ex","nucl-th"],"primary_cat":"astro-ph.HE","authors_text":"A. J. Dittmann, A. Parthasarathy, C. B. Markwardt, C. L. Baker, E. Fonseca, F. K. Lamb, H. T. Cromartie, I. Cognard, I. Stairs, J. M. Lattimer, K. C. Gendreau, L. Guillemot, M. C. Miller, M. Kerr, M. Loewenstein, M. T. Wolff, P. S. Ray, S. Bogdanov, S. Guillot, S. Manthripragada, S. M. Morsink, S. Pollard, S. Ransom, T. Cazeau, T. Okajima, T. T. Pennucci, W. C. G. Ho, Z. Arzoumanian","submitted_at":"2021-05-14T17:33:32Z","abstract_excerpt":"PSR J0740$+$6620 has a gravitational mass of $2.08\\pm 0.07~M_\\odot$, 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 $13.7^{+2.6}_{-1.5}$ km (68%). We apply our measurement, combine"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"We find that the equatorial circumferential radius of PSR J0740+6620 is 13.7^{+2.6}_{-1.5} km (68%). When all measurements are included the radius of a 1.4 M_⊙ neutron star is known to ±4% and the radius of a 2.08 M_⊙ neutron star is known to ±5%.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"The radius inference assumes specific geometries and temperature distributions for the rotating hot spots plus a particular model for the neutron-star atmosphere and beaming; if these are incorrect the reported credible intervals would shift.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"PSR J0740+6620 has an equatorial radius of 13.7^{+2.6}_{-1.5} km, and multi-messenger data constrain 1.4 and 2.08 solar-mass neutron star radii to 12.45 and 12.35 km respectively.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"The highest-mass neutron star with a reliable radius measurement has an equatorial circumference of 13.7 km.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"e37eda48c3188b8b6da01d1db8b182a4534562821e0093897f4e7895276bdf12"},"source":{"id":"2105.06979","kind":"arxiv","version":1},"verdict":{"id":"6c239ac9-cadf-4948-a1bb-77d8ac3f1e4f","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-17T06:54:17.506067Z","strongest_claim":"We find that the equatorial circumferential radius of PSR J0740+6620 is 13.7^{+2.6}_{-1.5} km (68%). When all measurements are included the radius of a 1.4 M_⊙ neutron star is known to ±4% and the radius of a 2.08 M_⊙ neutron star is known to ±5%.","one_line_summary":"PSR J0740+6620 has an equatorial radius of 13.7^{+2.6}_{-1.5} km, and multi-messenger data constrain 1.4 and 2.08 solar-mass neutron star radii to 12.45 and 12.35 km respectively.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"The radius inference assumes specific geometries and temperature distributions for the rotating hot spots plus a particular model for the neutron-star atmosphere and beaming; if these are incorrect the reported credible intervals would shift.","pith_extraction_headline":"The highest-mass neutron star with a reliable radius measurement has an equatorial circumference of 13.7 km."},"references":{"count":130,"sample":[{"doi":"","year":2017,"title":"P., Abbott , R., Abbott , T","work_id":"d2a199c7-3e4f-494a-a673-fd35e35cd2b5","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2018,"title":"2018, Physical Review Letters, 121, 161101","work_id":"697ee3a9-b9ca-4a1a-9ca0-75a8debd07b3","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2020,"title":"2020 a , , 892, L3","work_id":"eed0d4ad-b589-4d61-b4b2-2de60571da07","ref_index":3,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2020,"title":"2020 b , , 896, L44","work_id":"3b726685-52da-4ce9-a7a1-60bb0bcf8e71","ref_index":4,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"","year":2021,"title":"2021, arXiv e-prints, arXiv:2102.10767","work_id":"6d583897-8daa-4f36-b492-e1f260ac67e6","ref_index":5,"cited_arxiv_id":"","is_internal_anchor":false}],"resolved_work":130,"snapshot_sha256":"9da541b9060d90bb69d0b7d520b46ca01f0a228bed76bd6be141fc6758a3cd2e","internal_anchors":0},"formal_canon":{"evidence_count":2,"snapshot_sha256":"061870db7e82bf9c67924296c6a45a09dbfb9a8b52e45b822bed74afbf25c76f"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}