Chirenti, C., Dichiara, S., Lien, A. et al. Kilohertz quasiperiodic oscillations in short gamma-ray bursts. Nature (2023). https://doi.org/10.1038/s41586-022-05497-0

Findings in title quoted from the linked summary released by NASA, 9 Jan. 2023.

Excerpt:

>A neutron star forms when the core of a massive star runs out of fuel and collapses. This produces a shock wave that blows away the rest of the star in a supernova explosion.

>Neutron stars typically pack more mass than our Sun into a ball about the size of a city, but above a certain mass, they must collapse into black holes.

>Both the Compton data and computer simulations revealed mega neutron stars tipping the scales by 20% more than the most massive, precisely measured neutron star known – dubbed J0740+6620 – which weighs in at nearly 2.1 times the Sun’s mass.

>Superheavy neutron stars also have nearly twice the size of a typical neutron star, or about twice the length of Manhattan Island.

> 

>Computer simulations of these mergers show that gravitational waves exhibit a sudden jump in frequency – exceeding 1,000 hertz – as the neutron stars coalesce.

>These signals are too fast and faint for existing gravitational wave observatories to detect. But [lead author] Chirenti and her team reasoned that similar signals could appear in the gamma-ray emission from short GRBs.

>The mega neutron stars spin nearly 78,000 times a minute – almost twice the speed of J1748–2446ad, the fastest pulsar on record. This rapid rotation briefly supports the objects against further collapse, allowing them to exist for just a few tenths of a second, after which they proceed to form a black hole faster than the blink of an eye.

>While no gamma-ray QPOs materialized in the Swift and Fermi bursts, two short GRBs recorded by Compton’s Burst And Transient Source Experiment (BATSE) on July 11, 1991, and Nov. 1, 1993, fit the bill.

Banner: Merging neutron stars, illustrated here, produce a blast of gamma rays when they come together and collapse into a black hole. Observations of two bursts by NASA's Compton mission indicate that before their final collapse, the objects briefly form a single supersized neutron star. Credit: NASA's Goddard Space Flight Center/CI Lab. Editor: Francis Reddy