A More Precise Measurement of the Radius of PSR J0740+6620 Using Updated NICER Data

Alexander J. Dittmann; M. Coleman Miller; Frederick K. Lamb; Isiah M. Holt; Cecilia Chirenti; Michael T. Wolff; Slavko Bogdanov; Sebastien Guillot; Wynn C. G. Ho; Sharon M. Morsink; Zaven Arzoumanian; Keith C. Gendreau

doi:10.3847/1538-4357/ad5f1e

The Astrophysical Journal (Jan 2024)

A More Precise Measurement of the Radius of PSR J0740+6620 Using Updated NICER Data

Alexander J. Dittmann,
M. Coleman Miller,
Frederick K. Lamb,
Isiah M. Holt,
Cecilia Chirenti,
Michael T. Wolff,
Slavko Bogdanov,
Sebastien Guillot,
Wynn C. G. Ho,
Sharon M. Morsink,
Zaven Arzoumanian,
Keith C. Gendreau

Affiliations

Alexander J. Dittmann: ORCiD; Department of Astronomy and Joint Space-Science Institute, University of Maryland , College Park, MD 20742-2421, USA ; [email protected]; Theoretical Division, Los Alamos National Laboratory , Los Alamos, NM 87545, USA
M. Coleman Miller: ORCiD; Department of Astronomy and Joint Space-Science Institute, University of Maryland , College Park, MD 20742-2421, USA ; [email protected]
Frederick K. Lamb: ORCiD; Illinois Center for Advanced Studies of the Universe and Department of Physics, University of Illinois at Urbana-Champaign , 1110 West Green Street, Urbana, IL 61801-3080, USA; Department of Astronomy, University of Illinois at Urbana-Champaign , 1002 West Green Street, Urbana, IL 61801-3074, USA
Isiah M. Holt: ORCiD; Department of Astronomy and Joint Space-Science Institute, University of Maryland , College Park, MD 20742-2421, USA ; [email protected]; X-Ray Astrophysics Laboratory, NASA Goddard Space Flight Center , Code 662, Greenbelt, MD 20771, USA
Cecilia Chirenti: ORCiD; Department of Astronomy and Joint Space-Science Institute, University of Maryland , College Park, MD 20742-2421, USA ; [email protected]; Astroparticle Physics Laboratory, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA; Center for Research and Exploration in Space Science and Technology, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA; Center for Mathematics, Computation, and Cognition, UFABC , Santo André, SP 09210-170, Brazil
Michael T. Wolff: ORCiD; Space Science Division, U.S. Naval Research Laboratory , Washington, DC 20375-5352, USA
Slavko Bogdanov: ORCiD; Columbia Astrophysics Laboratory, Columbia University , 550 West 120th Street, New York, NY 10027, USA
Sebastien Guillot: ORCiD; Institut de Recherche en Astrophysique et Planétologie , UPS-OMP, CNRS, CNES, 9 avenue du Colonel Roche, BP 44346, F-31028 Toulouse Cedex 4, France
Wynn C. G. Ho: ORCiD; Department of Physics and Astronomy, Haverford College , 370 Lancaster Avenue, Haverford, PA 19041, USA
Sharon M. Morsink: ORCiD; Department of Physics, University of Alberta , Edmonton, AB, T6G 2E1, Canada
Zaven Arzoumanian: X-Ray Astrophysics Laboratory, NASA Goddard Space Flight Center , Code 662, Greenbelt, MD 20771, USA
Keith C. Gendreau: ORCiD; X-Ray Astrophysics Laboratory, NASA Goddard Space Flight Center , Code 662, Greenbelt, MD 20771, USA

DOI: https://doi.org/10.3847/1538-4357/ad5f1e
Journal volume & issue: Vol. 974, no. 2
p. 295

Abstract

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PSR J0740+6620 is the neutron star with the highest precisely determined mass, inferred from radio observations to be 2.08 ± 0.07 M _⊙ . Measurements of its radius therefore hold promise to constrain the properties of the cold, catalyzed, high-density matter in neutron star cores. Previously, Miller et al. and Riley et al. reported measurements of the radius of PSR J0740+6620 based on Neutron Star Interior Composition Explorer (NICER) observations accumulated through 2020 April 17, and an exploratory analysis utilizing NICER background estimates and a data set accumulated through 2021 December 28 was presented in Salmi et al. Here we report an updated radius measurement, derived by fitting models of X-ray emission from the neutron star surface to NICER data accumulated through 2022 April 21, totaling ∼1.1 Ms additional exposure compared to the data set analyzed in Miller et al. and Riley et al., and to data from XMM-Newton observations. We find that the equatorial circumferential radius of PSR J0740+6620 is ${12.92}_{-1.13}^{+2.09}$ km (68% credibility), a fractional uncertainty ∼83% the width of that reported in Miller et al., in line with statistical expectations given the additional data. If we were to require the radius to be less than 16 km, as was done in Salmi et al., then our 68% credible region would become $R={12.76}_{-1.02}^{+1.49}$ km, which is close to the headline result of Salmi et al. Our updated measurements, along with other laboratory and astrophysical constraints, imply a slightly softer equation of state than that inferred from our previous measurements.

Published in The Astrophysical Journal

ISSN: 1538-4357 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Astronomy: Astrophysics
Website: https://iopscience.iop.org/journal/0004-637X

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