Photo voltaic system hit by a pulse of intense radiation Unbelievable gamma-ray burst of 1 in 10,000 years

This chart compares the BOATs prompt emission to that of five previous record-holding long gamma-ray bursts. The BOAT was so bright it effectively blinded most gamma-ray instruments in space, but U.S. scientists were able to reconstruct its true brightness from Fermi data. Credit: NASAs Goddard Space Flight Center and Adam Goldstein (USRA)

With this type of GRB, astronomers 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 thats just a few degrees above the plane of our own galaxy, where thick dust clouds can greatly dim incoming light.

We cannot say conclusively that there is a supernova, which is surprising given the bursts brightness, said Andrew Levan, a professor of astrophysics at Radboud University in Nijmegen, Netherlands. Since dust clouds become more transparent at infrared wavelengths, Levan led near- and mid-infrared observations using NASAs James Webb Space Telescope its first use for this kind of study as well as the Hubble Space Telescope to spot the supernova. If its there, its very faint. We plan to keep looking, he added, but its possible the entire star collapsed straight into the black hole instead of exploding. Additional Webb and Hubble observations are planned over the next few months.

As the jets continue to expand into material surrounding the doomed star, they produce a multiwavelength afterglow that gradually fades away.

This illustration shows the ingredients of a long gamma-ray burst, the most common type. The core of a massive star (left) has collapsed, forming a black hole that sends a jet of particles moving through the collapsing star and out into space at nearly the speed of light. Radiation across the spectrum arises from hot ionized gas (plasma) in the vicinity of the newborn black hole, collisions among shells of fast-moving gas within the jet (internal shock waves), and from the leading edge of the jet as it sweeps up and interacts with its surroundings (external shock). Credit: NASAs Goddard Space Flight Center

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 whats 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 dont 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.

The jets themselves were not unusually powerful, but they were exceptionally narrow much like the jet setting of a garden hose and one was pointed directly at us, Alexander explained. The closer to head-on we view a jet, the brighter it appears. Although the afterglow was unexpectedly dim at radio energies, its likely that GRB 221009A will remain detectable for years, providing a novel opportunity to track the full life cycle of a powerful jet.

XMM-Newton images recorded 20 dust rings, 19 of which are shown here in arbitrary colors. This composite merges observations made two and five days after GRB 221009A erupted. Dark stripes indicate gaps between the detectors. A detailed analysis shows that the widest ring visible here, comparable to the apparent size of a full moon, came from dust clouds located about 1,300 light-years away. The innermost ring arose from dust at a distance of 61,000 light-years on the other side of our galaxy. GRB221009A is only the seventh gamma-ray burst to display X-ray rings, and it triples the number previously seen around one. Credit: ESA/XMM-Newton/M. Rigoselli (INAF)

The burst also enabled astronomers to probe distant dust clouds in our own galaxy. As the prompt X-rays traveled toward us, some of them reflected off of dust layers, creating extended light echoes of the initial blast in the form of X-ray rings expanding from the bursts location. The X-ray Telescope on NASAs Neil Gehrels Swift Observatory discovered the presence of a series of echoes. Detailed follow-up by ESAs (the

Her team was able to probe the dust rings with NASAs Imaging X-ray Polarimetry Explorer to glimpse how the prompt emission was organized, which can give insights into how the jets form. In addition, a small degree of polarization observed in the afterglow phase confirms that we viewed the jet almost directly head-on.

Together with similar measurements now being studied by a team using data from ESAs INTEGRAL observatory, scientists say it may be possible to prove that the BOATs jets were powered by tapping into the energy of a magnetic field amplified by the black holes spin. Predictions based on such models have already successfully explained other aspects of this burst.

References:

Focus on the Ultra-luminous Gamma-Ray Burst GRB 221009A March 2023, The Astrophysical Journal Letters.