In a groundbreaking discovery, Chinese scientists have identified the highest-energy gamma-ray spectral line ever observed from cosmic celestial bodies, peaking at an astonishing 37 million electron volts. This remarkable finding promises to significantly advance our understanding of gamma-ray bursts (GRBs), some of the most violent and energetic phenomena in the universe.
The research team, led by experts from the Institute of High Energy Physics (IHEP) at the Chinese Academy of Sciences, unveiled their findings in the journal Science China Physics, Mechanics & Astronomy. Their study sheds new light on GRBs, which occur during cataclysmic events such as the collapse of massive stars or the merging of neutron stars and black holes.
During the main burst phase of the GRB studied, the energy of the spectral line reached unprecedented levels. “We discovered a spectral line in the energy spectrum of GRB 221009A featuring a power-law decay pattern for both the line energy and flux, and an almost constant and relatively narrow line width as the burst progresses,” explained Xiong Shaolin, the leader of the research team and principal investigator of the GECAM series space telescopes at IHEP.
The scientists achieved this breakthrough through joint observations utilizing both space-based and ground-based telescopes, including China’s first X-ray astronomy satellite, Insight-HXMT; the GECAM-C, an all-sky gamma-ray monitor dedicated to GRBs; and the Large High Altitude Air Shower Observatory, which operates in the very high energy gamma-ray band. By combining data from the GECAM-C space telescope and the Fermi Gamma-ray Space Telescope, they conducted a detailed spectral analysis of GRB 221009A.
The team faced significant challenges in extracting precise and reliable GRB spectra due to the extreme brightness of the burst. However, their comprehensive analyses of instrumental effects and background issues allowed them to successfully observe the gamma-ray spectral line at record-breaking energies.
GRBs have captivated astronomers since their first discovery in 1967. With the recent attention on gravitational waves, GRBs have become a focal point in multi-wavelength and multi-messenger time-domain astronomy. The GRB observed by the Chinese team, coded GRB 221009A, was the brightest ever recorded when it was detected worldwide on October 9, 2022, believed to be the result of a massive star’s collapse.
“This discovery holds great significance for studying the physics and mechanisms behind GRBs and the relativistic jets they launch,” noted Xiong Shaolin. The findings not only enhance our understanding of these powerful cosmic events but also underscore China’s growing capabilities in space-based astronomical observations.
To continue unveiling the mysteries of the extreme universe, China has launched a series of satellites dedicated to GRB observations, including Insight-HXMT, the GECAM series, the Einstein Probe, and the Space Variable Objects Monitor. These advanced instruments are positioning China at the forefront of high-energy astrophysics research.
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Chinese scientists discover highest-energy gamma-ray spectral line
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