New data on the brightest gamma-ray burst ever observed

New data on the brightest gamma-ray burst ever observed

2023-06-07 20:00:05

The explosions or gamma-ray bursts (GRBs), for its acronym in English) are, as their name suggests, highly energetic emissions at gamma wavelengths. In October 2022 the brightest of all was reported: GRB 221009Awhose jet or jet has been discussed in detail. The results are now presented in the journal Science Advances.

This bright flash likely arose from a jet propelled by a rapidly rotating black hole.

This bright burst probably originated from a “shallow structured jet” propelled by a massive black hole spinning at high speed, according to a novel analysis of the glow of this GRB.

“Our study reveals that the jet of GRB 221009A had a nucleus [central] narrow, with ‘wings’ [laterales] wider and more inclined that extended more than in the typical jets of gamma-ray bursts”, explains the first author to SINCBrendan O’Connorfrom George Washington University (USA), “this is probably a characteristic of the most energetic explosions.”

The astronomer highlights how exceptional this flash is: “GRB 221009A is the brightest gamma-ray burst to date. It is 70 times brighter than any other discovered in more than 50 years of observation. It is an extraordinary event that we have been very fortunate to observe in our lifetime.”

GRB 221009A is the brightest gamma-ray burst yet detected: it is 70 times more luminous than any other discovered in more than 50 years of observation.

Brendan O’Connor (Universidad George Washington)

Another of the authors Rosa Leticia Becerrafrom the National Autonomous University of Mexico, agrees: “Given the measured properties, it is estimated that an event like this happens every 1000 years, for which we have been extremely fortunate in having the necessary technology to detect it.”

Longer GRBs – which persist for more than a few seconds – are often caused by the explosive death of a rotating massive star. GRB 221009A is an outlier within this group. It was not only extraordinarily long, but unexpectedly bright at all frequencies, disturbing Earth’s ionosphere upon arrival.

It is estimated that such an event happens every 1,000 years, which is why we have been extremely fortunate to have the technology to detect it.

Rosa Leticia Becerra (UNAM)

Observations have been made with various satellites, such as the Fermi telescope from NASA. As time passes, the shock generated in a gamma-ray burst like this slows down, emitting at lower frequencies, such as X-rays, optical, and radio. In all these ranges, the event has also been followed with a multitude of instruments (Swift, XMM-NewtonHubble, Gemini, Lowell Discovery Telescope, Australia Telescope Compact Array…)

The researchers found that the decay rates of X-ray, optical, and infrared brightness levels during the afterglow of GRB 221009A, which lasted more than three months, did not evolve in the expected way. Its luminosity exceeded all other observed X-ray flares by an order of magnitude.

Collapsing star black hole

According to the team, this discrepancy would be reduced if the original jet were a “jet shallow structured”, and if it came from ‘magnetofluidic’ processes linked to a black hole (formed at the heart of a collapsing massive star) rapidly rotating, with a mass of about 5 solar masses.

The authors have concluded that similar bright, high-energy GRBs can be propelled by structured jets launched by a motor central common

GRB 221009A, given its energy and temporal evolution, allows us to resolve in more detail what happens within this type of event

“Due to the distances at which these events are found (outside our galaxy), many models they are capable of explaining the observations in a general way”, says Becerra, “but GRB 221009A, given its energy and temporal evolution, allows us to resolve in more detail what happens within these events. We have analyzed your geometryand it is much more complex than previously known for most GRBs.”

Regarding the next steps, the astronomer advances: “Once there are so many observations of an event, it is necessary to compare them with theoretical models. This gives the opportunity to restrict parameters such as the opening angles of the jetor the energy that is possible to produce in a GRB, and gives clues about the parents, that is, what star type (mass, metallicity, wind, loss of mass, magnetic field, rotation, etc) produced such an explosion”.

Rights: Creative Commons.

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