March 29, 2023
Scientists have confirmed that the brightest burst of gamma and X-rays ever recorded, GRB 221009A, was detected on October 9, 2022. The event was so bright that it effectively blinded most gamma-ray instruments in space. The scientists were able to reconstruct the intensity of the emission from the data captured by NASA’s Fermi Gamma-ray Space Telescope. They then compared their results with those from the Russian team working on Konus data and Chinese teams analyzing observations from their own instruments. They found that the burst was 70 times brighter than any previously seen, and likely the brightest burst at X-ray and gamma-ray energies to occur since human civilization began. The initial signal from the burst had been traveling for approximately 1.9 billion years before it reached Earth. The scientists think that these bursts represent the birth cries of black holes that form when the cores of massive stars collapse under their own weight.
Astronomers have been combing through the data gathered by various observatories to better understand the scientific impact of the event. The GRB 221009A observations span the spectrum, from radio waves to gamma rays, and include data from many NASA and partner missions. Papers describing the results presented at the High Energy Astrophysics Division meeting of the American Astronomical Society in Waikoloa, Hawaii, appear in a focus issue of The Astrophysical Journal Letters.
The scientists expect to find a brightening supernova a few weeks later, but so far it has proven elusive. One reason is that the GRB appeared in a part of the sky that’s just a few degrees above the plane of our own galaxy, where thick dust clouds can greatly dim incoming light. Additional observations are planned over the next few months.
“Being so close and so bright, this burst offered us an unprecedented opportunity to gather observations of the afterglow across the electromagnetic spectrum and to test how well our models reflect what’s really happening in GRB jets,” said Kate Alexander, an assistant professor in the department of astronomy at the University of Arizona in Tucson. “Twenty-five years of afterglow models that have worked very well cannot completely explain this jet,” she said. “In particular, we found a new radio component we don’t fully understand. This may indicate additional structure within the jet or suggest the need to revise our models of how GRB jets interact with their surroundings.”
GRB 221009A, also known as the BOAT burst, was an astronomical event that has captivated the attention of scientists around the world. The burst was first detected on October 9, 2022, by NASA's Fermi Gamma-ray Space Telescope, and quickly triggered detectors on numerous spacecraft and observatories around the globe.
The burst was so bright that it effectively blinded most gamma-ray instruments in space, making it difficult to record the real intensity of the emission. However, scientists from the United States, Russia, and China were able to reconstruct the information from the Fermi data and other observations.
The BOAT burst was found to be 70 times brighter than any previously seen burst at X-ray and gamma-ray energies, making it the brightest burst since human civilization began, according to Eric Burns, an assistant professor of physics and astronomy at Louisiana State University in Baton Rouge, who led an analysis of some 7,000 GRBs. The findings were presented at the High Energy Astrophysics Division meeting of the American Astronomical Society in Waikoloa, Hawaii.
Observations of the BOAT burst spanned the spectrum, from radio waves to gamma rays, and included data from many NASA and partner missions, such as the NICER X-ray telescope on the International Space Station and NASA's NuSTAR observatory. Voyager 1, which is currently in interstellar space, also contributed to the observations.
The BOAT burst was a type of GRB known as a "long" GRB, whose initial, or prompt, emission lasts more than two seconds. Astronomers believe that these bursts represent the birth cries of black holes formed when the cores of massive stars collapse under their own weight. As the black hole quickly ingests the surrounding matter, it blasts out jets in opposite directions containing particles accelerated to near the speed of light. These jets pierce through the star, emitting X-rays and gamma rays as they stream into space.
One interesting aspect of the BOAT burst is that, unlike most long GRBs, a brightening supernova was not detected in the weeks following the burst. This is surprising given the burst's brightness and suggests that the star may have collapsed straight into the black hole instead of exploding.
Scientists are continuing to study the BOAT burst and its afterglow across the electromagnetic spectrum to better understand the nature of GRB jets and their interactions with their surroundings. The burst has already challenged existing afterglow models, and additional observations with telescopes such as the James Webb Space Telescope and the Hubble Space Telescope are planned over the next few months.