Brightest gamma-ray burst of all time came from the collapse of a massive star

Now, a Northwestern-led crew has confirmed that the phenomenon answerable for the historic burst — dubbed the B.O.A.T. (“brightest of all time”) — is the collapse and subsequent explosion of an enormous star. The crew found the explosion, or supernova, utilizing NASA’s James Webb Area Telescope (JWST).

Whereas this discovery solves one thriller, one other thriller deepens.

The researchers speculated that proof of heavy parts, akin to platinum and gold, would possibly reside throughout the newly uncovered supernova. The intensive search, nevertheless, didn’t discover the signature that accompanies such parts. The origin of heavy parts within the universe continues to stay as certainly one of astronomy’s largest open questions.

The analysis can be printed on Friday (April 12) within the journal Nature Astronomy.

“Once we confirmed that the GRB was generated by the collapse of an enormous star, that gave us the chance to check a speculation for a way a few of the heaviest parts within the universe are shaped,” stated Northwestern’s Peter Blanchard, who led the examine. “We didn’t see signatures of those heavy parts, suggesting that extraordinarily energetic GRBs just like the B.O.A.T. don’t produce these parts. That does not imply that every one GRBs don’t produce them, nevertheless it’s a key piece of knowledge as we proceed to grasp the place these heavy parts come from. Future observations with JWST will decide if the B.O.A.T.’s ‘regular’ cousins produce these parts.”

Blanchard is a postdoctoral fellow at Northwestern’s Heart for Interdisciplinary Exploration and Analysis in Astrophysics (CIERA), the place he research superluminous supernovae and GRBs. The examine contains co-authors from the Heart for Astrophysics | Harvard & Smithsonian; College of Utah; Penn State; College of California, Berkeley; Radbound College within the Netherlands; Area Telescope Science Institute; College of Arizona/Steward Observatory; College of California, Santa Barbara; Columbia College; Flatiron Institute; College of Greifswald and the College of Guelph.

Beginning of the B.O.A.T.

When its gentle washed over Earth on Oct. 9, 2022, the B.O.A.T. was so shiny that it saturated many of the world’s gamma-ray detectors. The highly effective explosion occurred roughly 2.4 billion light-years away from Earth, within the path of the constellation Sagitta and lasted a number of hundred seconds in length. As astronomers scrambled to watch the origin of this extremely shiny phenomenon, they have been instantly hit with a way of awe.

“So long as we’ve got been in a position to detect GRBs, there isn’t any query that this GRB is the brightest we’ve got ever witnessed by an element of 10 or extra,” Wen-fai Fong, an affiliate professor of physics and astronomy at Northwestern’s Weinberg School of Arts and Sciences and member of CIERA, stated on the time.

“The occasion produced a few of the highest-energy photons ever recorded by satellites designed to detect gamma rays,” Blanchard stated. “This was an occasion that Earth sees solely as soon as each 10,000 years. We’re lucky to dwell in a time when we’ve got the know-how to detect these bursts occurring throughout the universe. It is so thrilling to watch such a uncommon astronomical phenomenon because the B.O.A.T. and work to grasp the physics behind this distinctive occasion.”

A ‘regular’ supernova

Slightly than observe the occasion instantly, Blanchard, his shut collaborator Ashley Villar of Harvard College and their crew needed to view the GRB throughout its later phases. About six months after the GRB was initially detected, Blanchard used the JWST to look at its aftermath.

“The GRB was so shiny that it obscured any potential supernova signature within the first weeks and months after the burst,” Blanchard stated. “At these instances, the so-called afterglow of the GRB was just like the headlights of a automobile coming straight at you, stopping you from seeing the automobile itself. So, we needed to look forward to it to fade considerably to provide us an opportunity of seeing the supernova.”

Blanchard used the JWST’s Close to Infrared Spectrograph to watch the item’s gentle at infrared wavelengths. That is when he noticed the attribute signature of parts like calcium and oxygen sometimes discovered inside a supernova. Surprisingly, it wasn’t exceptionally shiny — just like the extremely shiny GRB that it accompanied.

“It isn’t any brighter than earlier supernovae,” Blanchard stated. “It appears pretty regular within the context of different supernovae related to much less energetic GRBs. You would possibly anticipate that the identical collapsing star producing a really energetic and shiny GRB would additionally produce a really energetic and shiny supernova. But it surely seems that is not the case. We’ve this extraordinarily luminous GRB, however a traditional supernova.”

Lacking: Heavy parts

After confirming — for the primary time — the presence of the supernova, Blanchard and his collaborators then looked for proof of heavy parts inside it. At the moment, astrophysicists have an incomplete image of all of the mechanisms within the universe that may produce parts heavier than iron.

The first mechanism for producing heavy parts, the speedy neutron seize course of, requires a excessive focus of neutrons. To this point, astrophysicists have solely confirmed the manufacturing of heavy parts by way of this course of within the merger of two neutron stars, a collision detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2017. However scientists say there have to be different methods to supply these elusive supplies. There are just too many heavy parts within the universe and too few neutron-star mergers.

“There’s probably one other supply,” Blanchard stated. “It takes a really very long time for binary neutron stars to merge. Two stars in a binary system first must explode to go away behind neutron stars. Then, it may possibly take billions and billions of years for the 2 neutron stars to slowly get nearer and nearer and at last merge. However observations of very outdated stars point out that elements of the universe have been enriched with heavy metals earlier than most binary neutron stars would have had time to merge. That is pointing us to another channel.”

Astrophysicists have hypothesized that heavy parts additionally may be produced by the collapse of a quickly spinning, huge star — the precise kind of star that generated the B.O.A.T. Utilizing the infrared spectrum obtained by the JWST, Blanchard studied the interior layers of the supernova, the place the heavy parts ought to be shaped.

“The exploded materials of the star is opaque at early instances, so you’ll be able to solely see the outer layers,” Blanchard stated. “However as soon as it expands and cools, it turns into clear. Then you’ll be able to see the photons coming from the interior layer of the supernova.”

“Furthermore, completely different parts take up and emit photons at completely different wavelengths, relying on their atomic construction, giving every factor a singular spectral signature,” Blanchard defined. “Due to this fact, an object’s spectrum can inform us what parts are current. Upon analyzing the B.O.A.T.’s spectrum, we didn’t see any signature of heavy parts, suggesting excessive occasions like GRB 221009A will not be major sources. That is essential info as we proceed to attempt to pin down the place the heaviest parts are shaped.”

Why so shiny?

To tease aside the sunshine of the supernova from that of the brilliant afterglow that got here earlier than it, the researchers paired the JWST knowledge with observations from the Atacama Giant Millimeter/Submillimeter Array (ALMA) in Chile.

“Even a number of months after the burst was found, the afterglow was shiny sufficient to contribute plenty of gentle within the JWST spectra,” stated Tanmoy Laskar, an assistant professor of physics and astronomy on the College of Utah and a co-author on the examine. “Combining knowledge from the 2 telescopes helped us measure precisely how shiny the afterglow was on the time of our JWST observations and permit us to fastidiously extract the spectrum of the supernova.”

Though astrophysicists have but to uncover how a “regular” supernova and a record-breaking GRB have been produced by the identical collapsed star, Laskar stated it may be associated to the form and construction of the relativistic jets. When quickly spinning, huge stars collapse into black holes, they produce jets of fabric that launch at charges near the velocity of sunshine. If these jets are slender, they produce a extra centered — and brighter — beam of sunshine.

“It is like focusing a flashlight’s beam right into a slender column, versus a broad beam that washes throughout an entire wall,” Laskar stated. “In reality, this was one of many narrowest jets seen for a gamma-ray burst to date, which supplies us a touch as to why the afterglow appeared as shiny because it did. There could also be different elements accountable as properly, a query that researchers can be learning for years to come back.”

Extra clues additionally might come from future research of the galaxy wherein the B.O.A.T. occurred. “Along with a spectrum of the B.O.A.T. itself, we additionally obtained a spectrum of its ‘host’ galaxy,” Blanchard stated. “The spectrum exhibits indicators of intense star formation, hinting that the delivery surroundings of the unique star could also be completely different than earlier occasions.”

Group member Yijia Li, a graduate scholar at Penn State, modeled the spectrum of the galaxy, discovering that the B.O.A.T.’s host galaxy has the bottom metallicity, a measure of the abundance of parts heavier than hydrogen and helium, of all earlier GRB host galaxies. “That is one other distinctive facet of the B.O.A.T. that will assist clarify its properties,” Li stated.

The examine, “JWST detection of a supernova related to GRB 221009A with out an r-process signature,” was supported by NASA (award quantity JWST-GO-2784) and the Nationwide Science Basis (award numbers AST-2108676 and AST-2002577). This work relies on observations made with the NASA/ESA/CSA James Webb Area Telescope.