Chinese scientists from the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS) have discovered a gamma-ray line with an energy of up to 37 million electron volts from an extremely bright gamma-ray burst.

This represents the highest energy spectral line feature ever emitted by celestial objects in the universe.

The scientists have also discovered that the gamma-ray line follows a power-law function over time, offering crucial clues for unraveling the mystery of the line.

Their paper was featured on the cover of Science China Physics, Mechanics & Astronomy.

Most energetic explosion

Gamma-ray bursts (GRBs) are the most energetic explosions in the universe. They can be produced by the core collapse of a massive star or the collision of two compact stars, such as neutron stars and black holes.

The discoveries made by Chinese scientists were related to the brightest GRB of all time, known as GRB 221009A.

This gamma-ray burst (GRB) belongs to the former category and reached Earth on October 9, 2022. According to the IHEP, it was observed by numerous telescopes worldwide.

Researchers from the IHEP of the CAS, the Yunnan Observatories of CAS, Hebei Normal University, and Guizhou Normal University have come together to form a collaborative team.

They have conducted a thorough analysis of observation data from two space gamma-ray monitors, GECAM-C and Fermi/GBM.

“These findings provide new and important clues for unraveling the mysteries of gamma-ray bursts and relativistic jets, marking a milestone in the study of gamma-ray bursts,” head author of the paper Xiong Shaolin told China’s state-owned Global Times.

Detector suffered data loss

The GECAM-C, funded by CAS, accurately measured this GRB’s low-energy band spectrum, while the Fermi/GBM covered the high-energy band where the gamma-ray line appeared.

In particular, this burst is so bright (too many gamma-ray photons in a short period) that the Fermi/GBM detector suffered data loss during the bright part of the burst, making reliable data analysis very difficult.

GECAM-C did not experience such a problem thanks to its dedicated instrument design. Therefore, IHEP noted that the GECAM-C data were used to correct the Fermi/GBM data.

After conducting thorough analyses of the data issues, instrumental effects, and background modeling, the research group successfully obtained reliable spectra of the GRB.

They also identified a series of gamma-ray lines throughout the burst, including a surprising gamma-ray line with energy of up to 37 million electron volts, detected during the bright part of the burst.

Researchers discovered that line energy changes following a power-law function over time while the line width-to-line energy ratio remains nearly constant.

Such features offer compelling evidence of these gamma-ray lines’ reality and GRB origin.

According to the IHEP, these discoveries illuminate new and unique aspects of the physics of GRBs and their relativistic jets.

In a recent discovery of the highest-energy light coming from the Sun,

Michigan State University researchers showcased that gamma-ray energy could extend to the maximum TeV range – up to roughly 10 TeV.