The Radius of PSR J0740+6620 from NICER with NICER Background Estimates

Tuomo Salmi; Serena Vinciguerra; Devarshi Choudhury; Thomas E. Riley; Anna L. Watts; Ronald A. Remillard; Paul S. Ray; Slavko Bogdanov; Sebastien Guillot; Zaven Arzoumanian; Cecilia Chirenti; Alexander J. Dittmann; Keith C. Gendreau; Wynn C. G. Ho; M. Coleman Miller; Sharon M. Morsink; Zorawar Wadiasingh; Michael T. Wolff

doi:10.3847/1538-4357/ac983d

The Astrophysical Journal (Jan 2022)

The Radius of PSR J0740+6620 from NICER with NICER Background Estimates

Tuomo Salmi,
Serena Vinciguerra,
Devarshi Choudhury,
Thomas E. Riley,
Anna L. Watts,
Ronald A. Remillard,
Paul S. Ray,
Slavko Bogdanov,
Sebastien Guillot,
Zaven Arzoumanian,
Cecilia Chirenti,
Alexander J. Dittmann,
Keith C. Gendreau,
Wynn C. G. Ho,
M. Coleman Miller,
Sharon M. Morsink,
Zorawar Wadiasingh,
Michael T. Wolff

Affiliations

Tuomo Salmi: ORCiD; Anton Pannekoek Institute for Astronomy, University of Amsterdam , Science Park 904, 1090GE Amsterdam, The Netherlands ; [email protected]
Serena Vinciguerra: ORCiD; Anton Pannekoek Institute for Astronomy, University of Amsterdam , Science Park 904, 1090GE Amsterdam, The Netherlands ; [email protected]
Devarshi Choudhury: ORCiD; Anton Pannekoek Institute for Astronomy, University of Amsterdam , Science Park 904, 1090GE Amsterdam, The Netherlands ; [email protected]
Thomas E. Riley: ORCiD; Anton Pannekoek Institute for Astronomy, University of Amsterdam , Science Park 904, 1090GE Amsterdam, The Netherlands ; [email protected]
Anna L. Watts: ORCiD; Anton Pannekoek Institute for Astronomy, University of Amsterdam , Science Park 904, 1090GE Amsterdam, The Netherlands ; [email protected]
Ronald A. Remillard: ORCiD; MIT Kavli Institute for Astrophysics & Space Research , MIT, 70 Vassar Street, Cambridge, MA 02139, USA
Paul S. Ray: ORCiD; Space Science Division, U.S. Naval Research Laboratory , Washington, DC 20375, 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
Zaven Arzoumanian: 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; Astroparticle Physics Laboratory NASA/GSFC , Greenbelt, MD 20771, USA; Center for Research and Exploration in Space Science and Technology , NASA/GSFC, Greenbelt, MD 20771, USA; Center for Mathematics, Computation, and Cognition, UFABC , Santo André, SP 09210-170, Brazil
Alexander J. Dittmann: ORCiD; Department of Astronomy and Joint Space-Science Institute, University of Maryland , College Park, MD 20742-2421, USA; Theoretical Division, Los Alamos National Laboratory , Los Alamos, NM 87545, USA
Keith C. Gendreau: ORCiD; X-Ray Astrophysics Laboratory, NASA Goddard Space Flight Center , Code 662, Greenbelt, MD 20771, USA
Wynn C. G. Ho: ORCiD; Department of Physics and Astronomy, Haverford College , 370 Lancaster Avenue, Haverford, PA 19041, USA
M. Coleman Miller: ORCiD; Department of Astronomy and Joint Space-Science Institute, University of Maryland , College Park, MD 20742-2421, USA
Sharon M. Morsink: ORCiD; Department of Physics, University of Alberta , 4-183 CCIS, Edmonton, AB, T6G 2E1, Canada
Zorawar Wadiasingh: ORCiD; Center for Research and Exploration in Space Science and Technology , NASA/GSFC, Greenbelt, MD 20771, USA; Department of Astronomy, University of Maryland , College Park, Maryland 20742, USA; Astrophysics Science Division, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA
Michael T. Wolff: ORCiD; Space Science Division, U.S. Naval Research Laboratory , Washington, DC 20375, USA

DOI: https://doi.org/10.3847/1538-4357/ac983d
Journal volume & issue: Vol. 941, no. 2
p. 150

Abstract

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We report a revised analysis for the radius, mass, and hot surface regions of the massive millisecond pulsar PSR J0740+6620, studied previously with joint fits to NICER and XMM-Newton data by Riley et al. (2021) and Miller et al. (2021). We perform a similar Bayesian estimation for the pulse-profile model parameters, except that instead of fitting simultaneously the XMM-Newton data, we use the best available NICER background estimates to constrain the number of photons detected from the source. This approach eliminates any potential issues in the cross-calibration between these two instruments, providing thus an independent check of the robustness of the analysis. The obtained neutron star parameter constraints are compatible with the already published results, with a slight dependence on how conservative the imposed background limits are. A tighter lower limit causes the inferred radius to increase, and a tighter upper limit causes it to decrease. We also extend the study of the inferred emission geometry to examine the degree of deviation from antipodality of the hot regions. We show that there is a significant offset to an antipodal spot configuration, mainly due to the non-half-cycle azimuthal separation of the two emitting spots. The offset angle from the antipode is inferred to be above 25° with 84% probability. This seems to exclude a centered-dipolar magnetic field in PSR J0740+6620.

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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