Constraining the Neutron Star Mass–Radius Relation and Dense Matter Equation of State with NICER. I. The Millisecond Pulsar X-Ray Data Set

Abstract

We present the set of deep Neutron Star Interior Composition Explorer (NICER) X-ray timing observations of the nearby rotation-powered millisecond pulsars PSRs J0437−4715, J0030+0451, J1231−1411, and J2124−3358, selected as targets for constraining the mass-radius relation of neutron stars and the dense matter equation of state via modeling of their pulsed thermal X-ray emission. We describe the instrument, observations, and data processing/reduction procedures, as well as the series of investigations conducted to ensure that the properties of the data sets are suitable for parameter estimation analyses to produce reliable constraints on the neutron star mass-radius relation and the dense matter equation of state. We find that the long-term timing and flux behavior and the Fourier-domain properties of the event data do not exhibit any anomalies that could adversely affect the intended measurements. From phase-selected spectroscopy, we find that emission from the individual pulse peaks is well described by a single-temperature hydrogen atmosphere spectrum, with the exception of PSR J0437−4715, for which multiple temperatures are required.

Magnetohydrodynamic simulations of binary neutron star mergers in general relativity: Effects of magnetic field orientation on jet launching

“…These masses are consis-tent with astrophysical observations of NSs (see e.g. [13][14][15][16]), but it cannot rule out the presence of a stellar-mass BH [17]. Recently, X-ray observations have strongly suggested that the rapidly rotating, giant star 2MASS J05215658+4359220 is the binary companion of a noninteracting ∼ 3M BH [18].…”

A NICER View of PSR J0030+0451: Millisecond Pulsar Parameter Estimation

“…The NICERXTI data set d associated with the rotationpowered MSP PSRJ0030+0451 is necessarily a product of pre-processing, and its curation is largely described in Bogdanov et al (2019a). However, there are a number of details that are specific to each data set and so we record a summary of these details below.…”

“…The raw XTI event data are publicly available via the NICER archive (accessible via HEASARC 27 ). The processed data set d may be found in the persistent repository of Bogdanov et al (2019c).…”

“…In this section we describe model aspects that are generally shared between all models in the discrete set M. These model facets are in some cases described in detail elsewhere in the NICER literature (Bogdanov et al 2019a(Bogdanov et al , 2019b(Bogdanov et al , 2019c) and thus we are brief where possible. Due to the large number of symbols required to describe the models in this Letter, the symbols used to describe geometric variables shared with Bogdanov et al (2019b) are different; Table 1 provides symbol translation from Bogdanov et al (2019b), the theory in which underpins the present work.…”

“…Such background treatment is the default for NICER parameter estimation work and X-PSI (for implementation details see Appendix B of , and is based on Miller & Lamb (2015). In reality, the statistical properties of backgrounds do not exhibit time invariance, but exhibit long-term variation over the  1 ( ) year observation epoch of MSPs target by the NICER mission, especially due to factors such as dynamical space weather (Bogdanov et al 2019a). However, any background emission processes-and dynamical emission processes in the local vicinity of PSRJ0030+0451-that are not harmonically coupled to the surface X-ray emission will decohere over the unit phase interval whose boundary is periodic.…”