PSR J0030+0451 Mass and Radius from NICER Data and Implications for the Properties of Neutron Star Matter

• Published in: Astrophysical journal. Letters Vol. 887; no. 1; p. L24
• Main Authors: Miller, M. C., Lamb, F. K., Dittmann, A. J., Bogdanov, S., Arzoumanian, Z., Gendreau, K. C., Guillot, S., Harding, A. K., Ho, W. C. G., Lattimer, J. M., Ludlam, R. M., Mahmoodifar, S., Morsink, S. M., Ray, P. S., Strohmayer, T. E., Wood, K. S., Enoto, T., Foster, R., Okajima, T., Prigozhin, G., Soong, Y.
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center The American Astronomical Society 10.12.2019; AAS; IOP Publishing; Bristol : IOP Publishing
• Subjects: Astronomy; ASTRONOMY AND ASTROPHYSICS; Astrophysics; Bayesian analysis; Equations of state; Estimates; Millisecond pulsars; Neutron star cores; Neutron stars; Neutrons; Nuclear Theory; Physicists; Physics; Stars; Statistical inference; Stellar models; Stellar surfaces; Systematic errors; Waveforms; X-ray sources
• ISSN: 2041-8205; 2041-8213; 2041-8213
• DOI: 10.3847/2041-8213/ab50c5

Neutron stars are not only of astrophysical interest, but are also of great interest to nuclear physicists because their attributes can be used to determine the properties of the dense matter in their cores. One of the most informative approaches for determining the equation of state (EoS) of this dense matter is to measure both a star's equatorial circumferential radius Re and its gravitational mass M. Here we report estimates of the mass and radius of the isolated 205.53 Hz millisecond pulsar PSR J0030+0451 obtained using a Bayesian inference approach to analyze its energy-dependent thermal X-ray waveform, which was observed using the Neutron Star Interior Composition Explorer (NICER). This approach is thought to be less subject to systematic errors than other approaches for estimating neutron star radii. We explored a variety of emission patterns on the stellar surface. Our best-fit model has three oval, uniform-temperature emitting spots and provides an excellent description of the pulse waveform observed using NICER. The radius and mass estimates given by this model are km and (68%). The independent analysis reported in the companion paper by Riley et al. explores different emitting spot models, but finds spot shapes and locations and estimates of Re and M that are consistent with those found in this work. We show that our measurements of Re and M for PSR J0030+0451 improve the astrophysical constraints on the EoS of cold, catalyzed matter above nuclear saturation density.