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

Journal Article · Mon Dec 19 00:00:00 EST 2022 · The Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/ac983d· OSTI ID:1974948

Salmi, Tuomo ^[1]; Vinciguerra, Serena ^[1]; Choudhury, Devarshi ^[1]; Riley, Thomas E. ^[1]; Watts, Anna L. ^[1]; Remillard, Ronald A. ^[2]; Ray, Paul S. ^[3]; Bogdanov, Slavko ^[4]; Guillot, Sebastien ^[5]; Arzoumanian, Zaven ^[6]; Chirenti, Cecilia ^[7]; Dittmann, Alexander Joseph ^[8]; Gendreau, Keith C. ^[6]; Ho, Wynn C. G. ^[9]; Miller, M. Coleman ^[10]; Morsink, Sharon M. ^[9]; Wadiasingh, Zorawar ^[11]; Wolff, Michael T. ^[3]

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1. Univ. of Amsterdam (Netherlands)
2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
3. Naval Research Lab. (NRL), Washington, DC (United States)
4. Columbia Univ., New York, NY (United States)
5. Centre National de la Recherche Scientifique (CNRS) (France); Centre National d'Etudes Spatiales (CNES) (France)
6. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States)
7. Univ. of Maryland, College Park, MD (United States); NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Federal University of ABC (Brazil)
8. Univ. of Maryland, College Park, MD (United States); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
9. Haverford College, PA (United States)
10. Univ. of Maryland, College Park, MD (United States)
11. NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States); Univ. of Maryland, College Park, MD (United States)

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.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); USDOE Laboratory Directed Research and Development (LDRD) Program
• Grant/Contract Number: 89233218CNA000001
• OSTI ID: 1974948
• Report Number(s): LA-UR-22-28454
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 2 Vol. 941; ISSN 0004-637X
• Publisher: IOP Publishing
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
astronomy and astrophysics
neutron stars
x-ray astronomy