Using the X-ray data from NASA’s Neutron star Interior Composition Explorer (NICER), astronomers have produced a map of hot spots on the surface of a pulsar called PSR J0030+0451, a millisecond pulsar located approximately 1,174 light-years away in the constellation of Pisces, and obtained very precise measurements of a pulsar’s size and mass.
“In the simplest model, a pulsar has a powerful magnetic field shaped much like a household bar magnet,” the astronomers explained.
“The field is so strong it rips particles from the pulsar’s surface and accelerates them. Some particles follow the magnetic field and strike the opposite side, heating the surface and creating hot spots at the magnetic poles.”
“The whole pulsar glows faintly in X-rays, but the hot spots are brighter. As the object spins, these spots sweep in and out of view like the beams of a lighthouse, producing extremely regular variations in the object’s X-ray brightness.”
Using the NICER X-ray data, two research teams produced the mass and radius measurements of PSR J0030+0451 and also mapped its hot spots.
The first team, led by University of Amsterdam’s Professor Anna Watts and doctoral student Thomas Riley, determined PSR J0030+0451 is 1.3 times the Sun’s mass and 25.4 km (15.8 miles) across.
The second team, headed by University of Maryland’s Professor Cole Miller, found the pulsar is 1.4 times the Sun’s mass and is 26 km (16.2 miles) wide.
“When we first started working on PSR J0030+0451, our understanding of how to simulate pulsars was incomplete, and it still is. But thanks to NICER’s detailed data, open-source tools, high-performance computers and great teamwork, we now have a framework for developing more realistic models of these objects,” Riley said.
This image shows the Vela pulsar. Image credit: NASA / CXC / University of Toronto / M. Durant et al / DSS / Davide De Martin.
Our view from Earth looks onto the northern hemisphere of PSR J0030+0451.
When the astronomers mapped the shapes and locations of pulsar’s spots, they expected to find one there based on the textbook image of pulsars, but didn’t.
Instead, they identified up to three hot spots, all in the southern hemisphere.
“It’s remarkable, and also very reassuring, that the two teams achieved such similar sizes, masses and hot spot patterns for PSR J0030+0451 using different modeling approaches,” said NICER science team leader Dr. Zaven Arzoumanian, a researcher at NASA’s Goddard Space Flight Center.
“It tells us NICER is on the right path to help us answer an enduring question in astrophysics: What form does matter take in the ultra-dense cores of neutron stars?”
The findings were published in a series of papers in the Astrophysical Journal Letters.
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T.E. Riley et al. 2019. A NICER View of PSR J0030+0451: Millisecond Pulsar Parameter Estimation. ApJL 887, L21; doi: 10.3847/2041-8213/ab481c
G. Raaijmakers et al. 2019. A Nicer View of PSR J0030+0451: Implications for the Dense Matter Equation of State. ApJL 887, L22; doi: 10.3847/2041-8213/ab451a
A.V. Bilous et al. 2019. A NICER View of PSR J0030+0451: Evidence for a Global-scale Multipolar Magnetic Field. ApJL 887, L23; doi: 10.3847/2041-8213/ab53e7
M.C. Miller et al. 2019. PSR J0030+0451 Mass and Radius from NICER Data and Implications for the Properties of Neutron Star Matter. ApJL 887, L24; doi: 10.3847/2041-8213/ab50c5
Slavko Bogdanov et al. 2019. Constraining the Neutron Star Mass-Radius Relation and Dense Matter Equation of State with NICER. I. The Millisecond Pulsar X-Ray Data Set. ApJL 887, L25; doi: 10.3847/2041-8213/ab53eb
Slavko Bogdanov et al. 2019. Constraining the Neutron Star Mass–Radius Relation and Dense Matter Equation of State with NICER. II. Emission from Hot Spots on a Rapidly Rotating Neutron Star. ApJL 887, L26; doi: 10.3847/2041-8213/ab5968
Sebastien Guillot et al. 2019. NICER X-Ray Observations of Seven Nearby Rotation-powered Millisecond Pulsars. ApJL 887, L27; doi: 10.3847/2041-8213/ab511b
This article is based on text provided by the National Aeronautics and Space Administration.
