Illuminating Cosmic Enigmas: LHAASO’s Examination of Tera-Electronvolt Gamma-Ray Burst Afterglow

by Henrik Andersen
Gamma-Ray Burst (GRB) Analysis

The Large High Altitude Air Shower Observatory (LHAASO) team has reported a pioneering analysis on the gamma-ray burst (GRB) GRB 221009A, a celestial occurrence triggered by the detonation of a massive star two billion years prior.

The Large High Altitude Air Shower Observatory researchers have, for the first time, comprehensively traced the light trajectory of high-energy photons from a gamma-ray burst (GRB), consequently questioning existing theoretical models. Their observations of the extremely rare and luminous GRB 221009A, an explosion originating from a massive star two billion years prior, offers invaluable information for decoding GRB mechanisms.

Cutting-edge research insights on the gamma-ray burst (GRB) called GRB 221009A from the Large High Altitude Air Shower Observatory (LHAASO) were shared online by Science journal on June 8, 2023. The study, named “A tera-electronvolt afterglow from a narrow jet in an extremely bright GRB 221009A,” was completed by the international LHAASO collaboration team.

Two billion years in the past, a colossal star over 20 times the mass of the Sun exhausted its nuclear fusion energy, leading to its abrupt collapse and triggering an immense explosion. This unleashed a concentrated burst of cosmic pyrotechnics termed as a gamma-ray burst (GRB) that endured hundreds of seconds. The high-energy gamma-ray photons, created from the collision between the fireball and interstellar matter, journeyed through the enormous universe, heading directly towards Earth. On the night of October 9, 2022, at 13:20:50 UT, these photons reached the LHAASO’s field of view, where over 60,000 gamma-ray photons were collected. After several months of analysis, scientists finally revealed the specifics of this explosion event.

LHAASO successfully detected GRB 221009A at a significance level exceeding 250 standard deviations. Credit: Image by IHEP

For the first time, LHAASO accurately measured the full light curve of high-energy photons from a GRB’s afterglow

The photon flux collected by LHAASO points to its origin as the radiation following the primary burst. The primary burst, known as the prompt emission, is the initial massive explosion marked by intense low-energy gamma-ray radiation. The subsequent burst, the afterglow, is created when the ejected material crashes into the surrounding interstellar gas at speeds nearly matching that of light. “For the first time, LHAASO has precisely measured the full progression of the afterglow, encompassing the complete phase of tera-electronvolt gamma-ray flux from its rise to decay,” stated CAO Zhen, LHAASO project’s principal investigator, spokesperson for the LHAASO collaboration, and professor at the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences.

Considering the observations of tens of thousands of GRBs, scientists have developed theoretically perfect models and have robust confidence in them. LHAASO observed the complete high-energy light curve, a feat yet to be accomplished by other experiments, providing a robust database for precise testing of these theoretical models. Due to the rarity of such an event, likely occurring once in a millennium, it is expected that this observed result will remain among the best for several decades or even centuries to come.

For the first time, LHAASO measures the rapid enhancement process of high-energy photon flux from a GRB

“At the onset of the afterglow, LHAASO detected for the first time an extremely rapid.

Frequently Asked Questions (FAQs) about Gamma-Ray Burst (GRB) Analysis

What is the Large High Altitude Air Shower Observatory (LHAASO)?

The Large High Altitude Air Shower Observatory (LHAASO) is one of China’s significant national scientific and technological facilities. It conducts cosmic ray observation and research, situated on Haizi Mountain in Daocheng County, Sichuan Province.

What astronomical event did the LHAASO researchers analyze?

The LHAASO researchers analyzed a gamma-ray burst (GRB) named GRB 221009A, which is an explosion from a massive star that happened two billion years ago.

What are the key findings from the LHAASO research?

The LHAASO research discovered and detailed the complete light curve of high-energy photons from a GRB for the first time. This observation provides invaluable data for understanding GRB mechanisms and challenges existing theoretical models.

What significance does the GRB 221009A hold?

GRB 221009A was an extremely rare and bright event, providing an unprecedented opportunity to understand the nature of gamma-ray bursts. Its observation will remain one of the best for several decades or even centuries due to its rarity.

How does the LHAASO observatory work?

LHAASO consists of three kinds of arrays that facilitate wide-band and compound measurements of gamma rays and cosmic rays from high-energy celestial sources. It measures the secondary products of gamma rays or cosmic rays produced in the atmosphere, collecting Cherenkov light signals generated by these secondary particles in water.

What does the analysis of the GRB afterglow contribute to the scientific community?

The detailed analysis of the GRB afterglow, especially the measurement of the entire light curve of high-energy photons, provides a robust database for precise tests of theoretical models in astrophysics. It also prompts discussions within the scientific community about the mechanisms involved in GRBs.

More about Gamma-Ray Burst (GRB) Analysis

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NebulaNerd June 18, 2023 - 12:42 am

I wish there were more articles like this one! It’s complex but so so interesting. Just goes to show how much there is to discover in the universe.

Physics4Life June 18, 2023 - 3:13 am

Unbelievable results! The GRB mechanisms have always been a mystery. This study is an important step in the right direction.

CarlStarman June 18, 2023 - 6:37 am

The observation of tera-electronvolt gamma-ray afterglow is a breakthrough. Looking forward to more discoveries frm LHAASO team.

MikeTheExplorer June 18, 2023 - 6:53 am

Wow, i never thought we’d be able to get such detailed data from an event that happened so long ago. Science rocks!

SpaceLover101 June 18, 2023 - 12:32 pm

This gamma-ray burst is the brightest in history?! Wow, we humans were lucky to observe such a rare event. Great job LHAASO!

AstroJess June 18, 2023 - 7:18 pm

Read the article twice. So the star exploded billions of years ago and we’re just seeing the afterglow now? That’s mindblowing stuff.


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