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A NICER View of the Massive Pulsar PSR J0740+6620 Informed by Radio Timing and XMM-Newton Spectroscopy

Riley, Thomas E. and Watts, Anna L. and Ray, Paul S. and Bogdanov, Slavko and Guillot, Sebastien and Morsink, Sharon M. and Bilous, Anna V. and Arzoumanian, Zaven and Choudhury, Devarshi and Deneva, Julia S. and Gendreau, Keith C. and Harding, Alice K. and Ho, Wynn C. G. and Lattimer, James M. and Loewenstein, Michael and Ludlam, Renee M. and Markwardt, Craig B. and Okajima, Takashi and Prescod-Weinstein, Chanda and Remillard, Ronald A. and Wolff, Michael T. and Fonseca, Emmanuel and Cromartie, H. Thankful and Kerr, Matthew and Pennucci, Timothy T. and Parthasarathy, Aditya and Ransom, Scott and Stairs, Ingrid and Guillemot, Lucas and Cognard, Ismael (2021) A NICER View of the Massive Pulsar PSR J0740+6620 Informed by Radio Timing and XMM-Newton Spectroscopy. Astrophysical Journal Letters, 918 (2). Art. No. L27. ISSN 2041-8205. doi:10.3847/2041-8213/ac0a81.

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We report on Bayesian estimation of the radius, mass, and hot surface regions of the massive millisecond pulsar PSR J0740+6620, conditional on pulse-profile modeling of Neutron Star Interior Composition Explorer X-ray Timing Instrument event data. We condition on informative pulsar mass, distance, and orbital inclination priors derived from the joint North American Nanohertz Observatory for Gravitational Waves and Canadian Hydrogen Intensity Mapping Experiment/Pulsar wideband radio timing measurements of Fonseca et al. We use XMM-Newton European Photon Imaging Camera spectroscopic event data to inform our X-ray likelihood function. The prior support of the pulsar radius is truncated at 16 km to ensure coverage of current dense matter models. We assume conservative priors on instrument calibration uncertainty. We constrain the equatorial radius and mass of PSR J0740+6620 to be 12.39_(-0.98)^(+1.30) km and 2.072_(-0.066)}^(+0.067) M_⊙ respectively, each reported as the posterior credible interval bounded by the 16% and 84% quantiles, conditional on surface hot regions that are non-overlapping spherical caps of fully ionized hydrogen atmosphere with uniform effective temperature; a posteriori, the temperature is log₁₀(T[K] = 5.99_(-0.06)^(+0.05) for each hot region. All software for the X-ray modeling framework is open-source and all data, model, and sample information is publicly available, including analysis notebooks and model modules in the Python language. Our marginal likelihood function of mass and equatorial radius is proportional to the marginal joint posterior density of those parameters (within the prior support) and can thus be computed from the posterior samples.

Item Type:Article
Related URLs:
URLURL TypeDescription
Riley, Thomas E.0000-0001-9313-0493
Watts, Anna L.0000-0002-1009-2354
Ray, Paul S.0000-0002-5297-5278
Bogdanov, Slavko0000-0002-9870-2742
Guillot, Sebastien0000-0002-6449-106X
Morsink, Sharon M.0000-0003-4357-0575
Bilous, Anna V.0000-0002-7177-6987
Choudhury, Devarshi0000-0002-2651-5286
Deneva, Julia S.0000-0003-1226-0793
Gendreau, Keith C.0000-0001-7115-2819
Harding, Alice K.0000-0001-6119-859X
Ho, Wynn C. G.0000-0002-6089-6836
Lattimer, James M.0000-0002-5907-4552
Loewenstein, Michael0000-0002-1661-4029
Ludlam, Renee M.0000-0002-8961-939X
Markwardt, Craig B.0000-0001-9803-3879
Okajima, Takashi0000-0002-6054-3432
Prescod-Weinstein, Chanda0000-0002-6742-4532
Remillard, Ronald A.0000-0003-4815-0481
Wolff, Michael T.0000-0002-4013-5650
Fonseca, Emmanuel0000-0001-8384-5049
Cromartie, H. Thankful0000-0002-6039-692X
Kerr, Matthew0000-0002-0893-4073
Pennucci, Timothy T.0000-0001-5465-2889
Parthasarathy, Aditya0000-0002-4140-5616
Ransom, Scott0000-0001-5799-9714
Stairs, Ingrid0000-0001-9784-8670
Guillemot, Lucas0000-0002-9049-8716
Cognard, Ismael0000-0002-1775-9692
Additional Information:© 2021. The American Astronomical Society. Received 2021 April 16; revised 2021 June 9; accepted 2021 June 9; published 2021 September 8. This work was supported in part by NASA through the NICER mission and the Astrophysics Explorers Program. T.E.R. and A.L.W. acknowledge support from ERC Consolidator grant No. 865768 AEONS (PI: Watts). T.E.R. also acknowledges support from the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) through the VIDI and Projectruimte grants (PI: Nissanke). This work was sponsored by NWO Exact and Natural Sciences for the use of supercomputer facilities, and was carried out on the Dutch national e-infrastructure with the support of SURF Cooperative. This work was granted access to the HPC resources of CALMIP supercomputing center under the allocation 2016- P19056. S.B. was funded in part by NASA grants NNX17AC28G and 80NSSC20K0275. S.M.M. thanks NSERC for support. W.C.G.H. appreciates use of computer facilities at the Kavli Institute for Particle Astrophysics and Cosmology and acknowledges support through grant 80NSSC20K0278 from NASA. R.M.L. acknowledges the support of NASA through Hubble Fellowship Program grant HST-HF2-51440.001. Support for H.T.C. was provided by NASA through the NASA Hubble Fellowship Program grant #HST-HF2-51453.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. T.T.P. is a NANOGrav Physics Frontiers Center Postdoctoral Fellow funded by the National Science Foundation award number 1430284. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. S.M.R. is a CIFAR Fellow and is supported by the NSF Physics Frontiers Center award 1430284. Pulsar research at UBC is supported by an NSERC Discovery Grant and by the Canadian Institute for Advanced Research. This research has made extensive use of NASA's Astrophysics Data System Bibliographic Services (ADS) and the arXiv. We would also like to acknowledge the administrative and facilities staff whose labor supports our work. Facility: N - ICER XTI (Gendreau et al. 2016), NANOGrav, Green Bank Telescope, CHIME/Pulsar, XMM-Newton EPIC. Software: Python/C language (Oliphant 2007), GNU Scientific Library (GSL; Gough 2009), NumPy (van der Walt et al. 2011), Cython (Behnel et al. 2011), SciPy (Jones et al. 2001), OpenMP (Dagum & Menon 1998), MPI (Forum 1994), MPI for Python (Dalcín et al. 2008), Matplotlib (Hunter 2007; Droettboom et al. 2018), IPython (Perez & Granger 2007), Jupyter (Kluyver et al. 2016), tempo2 (photons; Hobbs et al. 2006), PINT (photonphase;, MultiNest (Feroz et al. 2009), PyMultiNest (Buchner et al. 2014), GetDist (Lewis 2019,, nestcheck (Higson 2018; Higson et al. 2018, 2019), fgivenx (Handley 2018), NICERsoft (, X-PSIv0.7 (; Riley 2021).
Funding AgencyGrant Number
European Research Council (ERC)865768
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
NASA Hubble FellowshipHST-HF2-51440.001
NASA Hubble FellowshipHST-HF2-51453.001
Canadian Institute for Advanced Research (CIFAR)UNSPECIFIED
Subject Keywords:Millisecond pulsars; Rotation powered pulsars; Pulsars; Radio pulsars; X-ray astronomy; Neutron stars
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Millisecond pulsars (1062); Rotation powered pulsars (1408); Pulsars (1306); Radio pulsars (1353); X-ray astronomy (1810); Neutron stars (1108)
Record Number:CaltechAUTHORS:20210914-225409705
Persistent URL:
Official Citation:Thomas E. Riley et al 2021 ApJL 918 L27
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110902
Deposited By: George Porter
Deposited On:14 Sep 2021 23:52
Last Modified:14 Sep 2021 23:52

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