Merged neutron stars, pictured here, produce a gamma-ray burst when they come together and collapse into a black hole. Observations of two explosions made by NASA’s Compton mission indicate that before their final collapse, the objects briefly form a single large neutron star. Credit: NASA Goddard Space Flight Center/CI Lab

Short gamma-ray bursts (GRBs) are associated with binary neutron star mergers, multi-messenger astronomical events observed in gravitational waves and in the multiband electromagnetic spectrum. Depending on the masses of the stars in the binary and the details of their largely unknown equation of state, a short-lived, dynamically evolving neutron star may form after the merger.

Astronomers who have been examining old data about explosions known as short gamma-ray bursts (GRBs) have found light patterns that suggest a superheavy neutron star existed briefly before collapsing into a black hole. The collision of two neutron stars likely created this fleeting massive object.

Cecilia Chirenti, a researcher at the University of Maryland, College Park (UMCP) and NASA Goddard Space Flight Center in Greenbelt, Maryland, stated: “We looked for these signals in 700 short GRBs detected with NASA’s Neil Gehrels Swift Observatory. , the Fermi Gamma-ray Space Telescope, and the Compton Gamma-ray Observatory. We found these gamma-ray patterns in two bursts observed by Compton in the early 1990s.”

Compton’s measurements and computer simulations showed that the mass of neutron megastars was 20% greater than that of the most precisely measured, most massive neutron star, J0740+6620, which is nearly 2.1 times as massive. from the Sun. Also, compared to normal neutron stars, superheavy neutron stars are nearly twice as large, or about twice the length of Manhattan Island.

Neutron megastars spin about 78,000 times per minute, nearly twice as fast as J1748-2446ad, the fastest pulsar yet observed. This rapid spin prevents them from collapsing further for only a few tenths of a second before proceeding to form a faster-than-light black hole.

Cole Miller, UMCP professor of astronomy and co-author of the paper, says: “We know that short GRBs form when orbiting neutron stars collide with each other, and we know that they end up collapsing into a black hole, but the precise sequence of the The events are not well understood. At some point, the fledgling 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 know more about how it unfolds. “.