Scientists have long been intrigued by X-ray binary star systems in which two stars orbit each other, with one of the two stars being either a black hole or a neutron star.
Both black holes and neutron stars are formed in supernova explosions and are very dense, giving them a strong gravitational pull. This makes them capable of capturing the outer layers of an ordinary star that orbits around them in a binary system, and this process looks like a rotating disk of matter (simulating a whirlpool) around a black hole/neutron star.
According to theoretical calculations, these spinning disks should show dynamic instability: about once an hour, the inner parts of the disk fall rapidly onto the black hole/neutron star, after which these inner regions fill up again, and the process repeats. Until now, this violent and extreme process has been directly observed only once in a binary system of black holes. It was first seen in a binary neutron star system called Swift J1858.6-0814. The new discovery demonstrates that this instability is a common property of these disks (and not caused by the presence of a black hole).
This phenomenon was captured by combining data from five ground-based and space-based telescopes covering multiple wavelengths. The scientific group, which is an international collaboration of astronomers led by the Canary Institute of Astrophysics, was formed specifically when the neutron star system was first discovered in 2018.
The study “General Accretion Instability of Black Holes and Neutron Stars” is published in the journal Nature.
Source: FM Vincentelli et al, A shared accretion instability for black holes and neutron stars, Nature (2023). DOI: 10.1038/s41586-022-05648-3
