NICER / ISS Science Nugget for July 11, 2019

NICER's first neutron star radius measurement to be submitted soon

Submission for publication is imminent (within 7-10 days) of two papers that represent NICER's first measurement of a neutron star radius and the first-ever precision measurement of mass and radius together for the same object — PSR J0030+0451, a pulsar with a 4.9 millisecond rotation period at a distance of 320 parsecs (approximately 1,000 light-years). The two manuscripts were prepared by members of the NICER Science Team carrying out independent analyses of the same data, and they produce consistent results despite differences in the assumptions they make in modeling the star's surface emission properties.

Additional "firsts" for these papers include estimating the mass of a solitary (i.e., not in a binary system) neutron star, and demonstrating unambiguously that its magnetic-field geometry is not that of a simple dipole. Shown in the figure is an energy spectrum of more than 1.9 Msec of NICER data acquired for PSR J0030+0451 that were used for these first NICER Equation of State (EOS) results.

PSR J0030+0451 energy spectrum from more than 1.9 Msec of NICER data

Figure: The energy spectrum of photons collected from the pulsar PSR J0030+0451 (red) compared to a model of the background (green) estimated for the period of time NICER accumulated these data. Over 1.9 Msec of exposure on this pulsar was collected over nearly 18 months, interspersed with observations of hundreds of celestial targets, including several other millisecond pulsars for which NICER will produce comparable neutron star radius measurements.

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