A NICER View of the Nearest and Brightest Millisecond Pulsar: PSR J0437–4715
Remillard, Ronald A.; Bogdanov, Slavko; Salmi, Tuomo; Ray, Paul S.; Watts, Anna L.; Choudhury, Devarshi; Kini, Yves; Vinciguerra, Serena; Arzoumanian, Zaven; Guillot, Sebastien; Ho, Wynn C. G.; Morsink, Sharon M.; Gendreau, Keith C.; Bilous, Anna V.; Riley, Thomas E.; Huppenkothen, Daniela; Lattimer, James M.; Dorsman, Bas; Reardon, Daniel J.; Rutherford, Nathan
Netherlands, United States, France, Australia, Canada
Abstract
We report Bayesian inference of the mass, radius, and hot X-ray emitting region properties—using data from the Neutron Star Interior Composition ExploreR (NICER)—for the brightest rotation-powered millisecond X-ray pulsar, PSR J0437‑4715. Our modeling is conditional on informative tight priors on mass, distance, and binary inclination obtained from radio pulsar timing using the Parkes Pulsar Timing Array (PPTA; Reardon et al.), and we use NICER background models to constrain the nonsource background, cross-checking with data from XMM-Newton. We assume two distinct hot emitting regions and various parameterized hot region geometries that are defined in terms of overlapping circles; while simplified, these capture many of the possibilities suggested by detailed modeling of return current heating. For the preferred model identified by our analysis, we infer a mass of M = 1.418 ± 0.037 M ⊙ (largely informed by the PPTA mass prior) and an equatorial radius of