NICER / ISS Science Nugget for November 3, 2017
X-ray Pulsations Discovered from PSR J1231-1411
NICER has discovered X-ray pulsations from a neutron star spinning at 271 rotations per second (more than 16,000 RPM). This star is the millisecond pulsar PSR J1231-1411, which packs about 1.5 times the mass of our Sun into a sphere about 15 miles in diameter. The NICER observations show that the rapid spin of the pulsar is causing particles to be accelerated in its magnetosphere and to rain down onto the magnetic polar caps with enough energy to heat them to approximately 1 million degrees Celsius, hot enough to glow in X-rays. NICER sees sinusoidal X-ray brightness pulsations as the polar caps rotate in and out of our view.
This is an important discovery for NICER because one of the mission's key science goals is to measure the radius of neutron stars by studying pulsed emission from the surface. Prior to NICER's launch, only a few suitable pulsars were known. This discovery adds a new source for these studies that will help constrain the nature of (stable) matter at super-nuclear densities, a regime that cannot be probed in Earth-based experiments.