NICER finds X-ray pulsar in record-fast orbit

NICER finds X-ray pulsar in record-fast orbit

Scientists analyzing information from the NICER mission have identified two stars spinning around each other every 38 minutes. One of the stars IGR J17062-6143 (J17062) is a rapidly rotating pulsar. This discovery provides a stellar pair with a record short orbital period in the binary pulsar class.

The data show that the stars J17062 are 300,000 km apart, which is less than the Earth-Moon distance. Based on the orbital period and remoteness, there is an assumption that the second object is a white dwarf rich in hydrogen.

An early 20-minute observation of RXTE in 2008 allowed the lower limit of the orbital period to be set to J17062. NICER, installed aboard the ISS in 2017, was able to monitor the system for a longer period of time. In August, the device tracked objects for more than 7 hours for 5.3 days. By combining all the information it turned out to confirm the record speed of the orbital rotation.

When a massive star goes into a supernova, its core collapses into a black hole or neutron star. The latter are so hot that they emit bright UV-light that enters the X-ray part of the EM spectrum. Pulsar is a rapidly rotating neutron star. A survey in 2008 showed that X-ray pulses are repeated 163 times per second. They mark the locations of hot spots around the magnetic poles of the pulsar, so they allow us to determine the rotation speed. J17062 rotates at a rate of 9800 revolutions per minute. Hot spots appear when the intense gravitational field of a neutron star pulls material away from its star neighbor, where it gathers in an accretion disk. Matter falls in a spiral and sneaks to the surface. Neutron stars are distinguished by powerful magnetic fields, so the material is scattered unevenly on the surface, moving along the magnetic field to the magnetic poles, where hot spots are created.

IGR stars J17062-6143 revolve around each other every 38 minutes - the fastest binary system with an auxifying millisecond X-ray pulsar

A steady stream of incident gas causes accelerated pulsars to spin faster. When rotating, hot spots appear and disappear in the X-ray instrument overview, like NICER. The speed of some pulsars reaches 700 revolutions per second, which is comparable to the blades of a kitchen mixer.

With time, material from a neighbor accumulates on the surface of a neutron star. As the atoms begin to merge, the energy equivalent of 100 bombs per 15 megatons is released. The analysis showed that the white dwarf reaches only 1.5% of the solar mass, and the pulsar - 1.4 solar masses. It is important to note that the distance between us and the pulsar is not a constant value. It varies with orbital motion. When the pulsar is closer, the X-rays come closer faster. The difference is only 8 milliseconds, but the sensitivity of NICER allows you to capture this value.

The NICER mission provides highly accurate measurements for the further study of the physics and behavior of neutron stars. Other results provided data on thermonuclear bursts of a single object, as well as observations of the accretion disk during this period.

Comments (0)