New examination discoveries on the gamma-beam burst (GRB) named GRB 221009A from the Enormous High Height Air Shower Observatory (LHAASO) were distributed web-based by the journal Science on June 8, 2023. The LHAASO international collaboration completed the study, which was titled “A tera-electron volt afterglow from a narrow jet in an extremely bright GRB 221009A.”
A collimated burst of cosmic fireworks known as a gamma-ray burst (GRB) that lasted hundreds of seconds was unleashed approximately two billion years ago when a massive star that was more than 20 times heavier than the sun used up the fusion energy that was in its nuclear fuel. As a result, the star collapsed immediately and caused a massive explosion.
The fireball’s collision with interstellar matter produced high-energy gamma-ray photons that sped through the vast universe and directly toward Earth. On the night of October 9, 2022, at 13:20:50 UT, these photons arrived at the field of perspective on LHAASO, where more than 60,000 gamma-beam photons were gathered. The specifics of this explosion event were finally revealed by scientists after several months of analysis.
The flux of photons collected by LHAASO indicates that they came from the radiation following the main burst, which is the first time that the entire light curve of high-energy photons from the afterglow of a GRB has been precisely measured for the first time. The initial massive explosion characterized by intense low-energy gamma-ray radiation is the main burst, or prompt emission. When the ejected matter travels at speeds very close to the speed of light and collides with the interstellar gas that surrounds it, the following burst, known as the afterglow, occurs.
Cao Zhen, principal investigator of the LHAASO project, spokesperson for the LHAASO collaboration, and professor at the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences, stated, “LHAASO accurately measured the complete process of the afterglow for the first time, comprising the complete phase of tera-electron-volt gamma-ray flux from rise to decay.”
LHAASO measured the intrinsic and observed spectra of photons five times. The energy range is around 0.2–7 TeV. Credit: IHEP
In view of the perception of a huge number of GRBs, researchers have developed apparently wonderful hypothetical models and have solid trust in them. For precise tests of these theoretical models, LHAASO provided the ideal data base by observing the entire high-energy light curve, which has yet to be reached by other experiments. It is anticipated that this observed result will continue to be one of the best for the next several decades or even centuries due to the rarity of this event, which probably occurs only once every millennium.
LHAASO measures for the first time the rapid enhancement process of high-energy photon flux from a GRB
“At the beginning of the onset of the afterglow, LHAASO detected for the first time the extremely rapid enhancement of photon flux,” stated Yao Zhiguo, a professor at IHEP and one of the corresponding authors of the paper. LHAASO measures for the first time the rapid enhancement process of high-energy photon flux from a GRB. Within a shorter time frame than two seconds, the transition expanded by an element of more than 100, trailed by a sluggish ascent that adjusted to the normal qualities of radiance. The early rapid enhancement phenomenon goes above and beyond what theoretical models had predicted.
This prompts an inquiry: What systems are really affecting everything? The distributed outcomes would start top-to-bottom conversations inside established researchers in regards to the systems associated with GRBs, including energy infusion, photon retention, and molecule speed increase.
Energy transition light bend and phantom file advancement of the glimmer radiation from GRB 221009A in the energy scope of 0.3-5 TeV, alongside the fitting capability. Credit: IHEP.
LHAASO was able to complete the first complete observation of the afterglow of a GRB above 100 GeV, revealing the rapid rising and rapid decay of GRB221009A’s afterglow for the first time.
GRB LHAASO observations have demonstrated that high-energy radiation decreases in brightness more rapidly around ten minutes after the beginning of the afterglow. “IHEP LHAASO reveals the mystery of the brightness of the brightest of all time.” According to Wang Xiangyu, a professor at Nanjing University and one of the corresponding authors of the paper, “this can be explained by the fact that the ejected material after the explosion forms a jet-like structure, and the rapid decrease in brightness occurs when the radiation angle extends to the edge of the jet.” Because of the incredibly early event of this splendor change, the deliberate point of the fly is induced to be tiny, just 0.8 degrees.
This is the smallest jet angle ever observed, indicating that the object observed is the brightest core of a typical internally bright and externally dark jet. Dai Zigao, a professor at the University of Science and Technology of China (CAS) and one of the corresponding authors of the paper, stated, “The observer happens to be directly facing the brightest core of the jet, and it naturally explains why this gamma-ray burst is the brightest in history and why such an event is so rare.” Dai Zigao is one of the corresponding authors of the paper.
LHAASO’s data-intensive observations at high-energy will reveal more mysteries
In the short time that this event lasted, the number of photons that LHAASO recorded exceeded the total number of photons that had been observed from the “standard candle” Crab Nebula over the previous few years. LHAASO’s data-intensive observations at high energy will shed more light on these mysteries. The number of photons could even reach 100,000 if the selection criteria were slightly looser!” said Zha Min, an IHEP professor and one of the paper’s corresponding authors.
In comparison, other instruments operating in a similar energy band have only detected photons tens of seconds after the burst and have only detected less than 1000 photons in other GRBs. “This burst event still has a lot of unknowns, and LHAASO scientists are still looking through the data to find out more. Please keep an eye out for the LHAASO analysis results,” Prof. Cao said.
More information: Cao Zhen et al, A tera–electron volt afterglow from a narrow jet in an extremely bright gamma-ray burst, Science (2023). DOI: 10.1126/science.adg9328
