NICER / ISS Science Nugget
for December 12, 2019

First NICER Key Science results released

NICER released its first set of key-science results this week, including a media feature and associated video to highlight the simultaneous publication of seven new peer-reviewed papers as a Focus Issue of The Astrophysical Journal Letters. Based on nearly two years of NICER data collection and months of supercomputer analysis for the millisecond-period pulsar J0030+0451, the papers provide:

  • the first precise (±10%, 1σ) mass and radius measurements for the same star
  • the first mass measurement for an isolated (i.e., non-binary) neutron star
  • the first map of surface "hot spot" locations, shapes, sizes, and temperatures, a guidepost to the star's magnetic field configuration
  • and,a new constraint on the state of matter in the cores of neutron stars, the densest matter anywhere in the universe.

Two groups within the NICER team independently analyzed a common dataset, arriving at virtually identical conclusions about the star's mass and radius, and revealing surprisingly that the star's magnetic polar caps are not located opposite each other on the star's surface (as would be expected from a simple magnetic dipole), but instead crowd together in the same hemisphere, the one opposite our line of sight. This effectively redraws textbook images of how pulsars work.

Mass-radius contours for PSR J0030+0451 from one of two independent
analyses of NICER data

Figure: Contours (68% probably inner, and 95% probability outer) for the mass and radius of PSR J0030+0451, based on the analysis reported in Miller et al. (ApJ Letters 887, L24), one of the independent analyses performed by the NICER team with approximately 2 million seconds of on-target exposure time.

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