Astronomers examined 700 short gamma-ray blasts (GRBs), which were detected by NASA’s Neil Gehrels Swift Observatory and Fermi Gamma-ray Space Telescope. Two short GRBs were able to detect flickering patterns in gamma radiation, which are called quasiperiodic oscillations. This indicates the existence of a neutron star that was superheavy just before its collapse into a black hole.
The center of the colorful gas disk is a neutron star (blue globe) that spins. Some of the gas follows the magnetic field’s blue lines and flows onto the object’s surfaces (blue-white arches). Image credit NASA’s Goddard Space Flight Center Conceptual Image Lab.
When the fuel in a star’s core runs out, a neutron star is formed. The shock waves created by this event can be used to blow away other stars in supernova explosions.
The mass of neutron stars is typically greater than that of our Sun, and they can be compressed into balls about the same size as a city. However, above a certain mass, these must fall into black holes.
Computer simulations and data from Compton’s Burst and Transient Source Eperiment (BATSE), both showed that neutron stars tipped the scales 20% higher than MSP J0740+6620, the largest known neutron star. This neutron star weighs nearly 2.1x the Sun’s.
The superheavy neutron stars are also nearly twice as large than a normal neutron star.
They spin almost 78,000 times per minute — nearly twice as fast than PSR J1748-2446ad which is the fastest known pulsar.
The objects are temporarily supported against further collapse by this rapid rotation. After that, they form a black hole much faster than you blink your eye.
Professor Cole Miller from the University of Maryland said that “we know that short GRBs are formed when orbiting neutron star collide together and we also know they ultimately collapse into a dark hole.”
“At some point the nascent dark hole explodes with a jet full of fast-moving particle that emits an intense flashes of gamma radiations. We want to know more about that process.”
Gravitational waves are created by merging neutron stars, which can be detectable by an increasing number of ground-based observatories.
Computer simulations reveal that these mergers result in a sharp jump in frequency, exceeding 1000 Hz. This is because neutron stars combine. These signals are too faint to be detected by existing gravitational-wave observatories.
The study authors argued that quasiperiodic oscillations, or similar signals could be seen in the gamma radiation from GRBs.
Two short GRB events, GRB 910711B and GRB 93101B, were detected in Compton/BATSE data on November 1st 1993 and July 11. 1991.
These results “are very important because they set the scene for future measurements hypermassive neutron star by gravitational waves observatories,” stated Dr. Chryssa Kuveliotou (an astronomer at George Washington University).
This week, the study was published in the journal. Nature.
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C. Chirenti The authors and others. In short gamma radiation bursts, quasiperiodic oscillations of the Kilohertz magnitude. Nature, published online January 9, 2023; doi: 10.1038/s41586-022-05497-0