Astronomers detect a gigantic neutron star that existed for only a fraction of a second

Reverberations in the fabric of space-time propagate throughout the universe, and astrophysicists are sometimes able to notice such shocks.

A team of astronomers has examined data on 700 short gamma-ray bursts (GRBs) detected with NASA’s Neil Gehrels Swift Observatory, the Fermi Gamma-ray Space Telescope, and the Compton Gamma-ray Observatory. They have discovered – in computer simulations – patterns of flickering gamma rays, called quasiperiodic oscillations, in two short GRBs that indicate the brief existence of a superheavy neutron star shortly before collapsing into a black hole.

This entire process lasted only a fraction of a second, as the researchers explain in their study published in the journal Nature, and can teach us a lot about the transient nature of neutron stars and the evolution of colossal black holes. When stars of a certain mass range explode as a supernova, they leave behind a dense core known as a neutron star. The pressures these ultra-dense objects create mean that a large amount of mass takes up little space. Thus, a neutron star can have a maximum mass of just over two suns, before collapsing under its own gravity and forming a black hole, so if the total of the two neutron stars falls below that limit, form a new neutron star; a giant.

should exist The giant neutron star explored in this scenario lasts only a few milliseconds, and simulations suggest that this hypermassive neutron star should exist. Gravitational wave detectors aren’t sensitive enough to show their presence, but gamma ray detectors can. The scientists searched for GRB signals in 700 short GRBs detected by NASA’s Neil Gehrels Swift Observatory, the Fermi Gamma-ray Space Telescope, and the Compton Gamma-ray Observatory. The researchers found gamma-ray patterns indicative of two neutron stars colliding and eventually forming a black hole in two bursts observed by Compton in the early 1990s.

“We know that short GRBs form when orbiting neutron stars collide with each other, and we know that they eventually collapse into a black hole, but the precise sequence of events is not well understood,” explains Cole Miller of the University of Maryland and study co-author. “At some point, the nascent black hole erupts with a jet of fast-moving particles that emits an intense flash of gamma rays, the highest-energy form of light, and we want to learn more about how it develops.” By the 2030s, gravitational-wave observatories are expected to become much more sensitive, so we may have a new perspective on the fleeting existence of giant-sized neutron stars.

Reference: C. Chirenti et al. Kilohertz quasiperiodic oscillations in short gamma-ray bursts. Nature, published online January 9, 2023; doi: 10.1038/s41586-022-05497-0