It's the BOAT: Astronomers observe 'brightest gamma-ray burst ever'

It’s the BOAT: Astronomers observe ‘brightest gamma-ray burst ever’

Gamma-ray burst GRB 221009A represents the birth of a new black hole formed in the core of a collapsing star, astronomers believe. Credit: NASA/Swift/Cruz de Wilde

On the morning of October 9, multiple space detectors detected a powerful gamma-ray burst (GRB) streaking across our solar system, sending astronomers around the world scrambling to train their telescopes on this part of the sky to collect vital data on the event. and its sequels. Dubbed GRB 221009A, astronomers say the gamma-ray burst is the strongest on record and could possibly be the “birth cry” of a new black hole. The event was quickly published in the Astronomer’s Telegram and observations are still ongoing.

“In our research group, we call this burst the ‘BOAT’ or brightest ever, because when you look at the thousands of bursts that gamma-ray telescopes have detected since the 1990s, this one stands out. said Jillian Rastinejad, a graduate student at Northwestern University.Rastinejad led one of two independent teams using the Gemini South telescope in Chile to study the afterglow of the event.

“This burst is much closer than typical GRBs, which is exciting because it allows us to detect many details that would otherwise be too faint to see,” said Roberta Pillera, graduate student at the Polytechnic University of Bari, Italy, and a member of the Fermi Large Area Telescope (LAT) collaboration. “But it’s also one of the most energetic and brightest bursts ever seen at any distance, which makes it doubly exciting.”

Gamma-ray bursts are very high-energy explosions in distant galaxies that last from milliseconds to hours. The first gamma-ray bursts were observed in the late 1960s, thanks to the launch of the Vela satellites by the United States. They were meant to detect telltale gamma-ray signatures of nuclear weapons testing following the 1963 nuclear test ban treaty with the Soviet Union. The United States feared that the Soviets were carrying out secret nuclear tests, in violation of the treaty. In July 1967, two such satellites picked up a flash of gamma radiation that was clearly not the signature of a nuclear weapons test.

Swift's X-ray telescope captured the afterglow of GRB 221009A about an hour after it was first detected.
Enlarge / Swift’s X-ray telescope captured the afterglow of GRB 221009A about an hour after it was first detected.

NASA/Swift/A. Beardmore (University of Leicester)

This data was classified, but later Vela satellites with improved instruments recorded several more gamma-ray bursts. A team from Los Alamos National Laboratory analyzed when each burst was detected by different satellites to estimate the position in the sky of 16 of those bursts. And they determined that the bursts did not originate from Earth or our solar system, publishing their findings in a 1973 paper in Astrophysical Journal.

There are two classes of gamma-ray bursts. Most (70%) are long bursts lasting longer than two seconds, often with a bright afterglow. These are usually linked to rapidly forming star-forming galaxies. Astronomers believe the long bursts are linked to the death of massive stars collapsing to form a neutron star or a black hole (or, alternatively, a newly formed magnetar). The baby black hole would produce jets of highly energetic particles moving near the speed of light, powerful enough to pierce the remnants of the progenitor star, emitting X-rays and gamma rays.

These gamma-ray bursts that last less than two seconds (about 30%) are considered short bursts, typically emitting from regions with very little star formation. Astronomers believe these gamma-ray bursts are the result of mergers between two neutron stars, or a neutron star merging with a black hole, including a “kilonova”.

This hypothesis was confirmed in 2017, when the LIGO collaboration picked up the gravitational wave signal of the merger of two neutron stars, accompanied by the powerful gamma-ray bursts associated with a kilonova. Earlier this year, astrophysicists spotted mysterious X-rays that they believe may be the first-ever detection of a kilonova “afterglow” from that same fusion. (Alternatively, this could be the first sighting of matter falling into the black hole that formed after the merger.)

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