Scientists Uncover Source of Rare Cosmic X-Ray Flash

The event, known as EP241107a, was first detected by China's Einstein Probe mission, a space observatory designed to monitor rapidly changing high-energy events across the universe.

Astronomers have identified the likely origin of a rare and mysterious cosmic explosion known as a Fast X-ray Transient (FXT), shedding new light on some of the most powerful events in the universe. The findings come from an international study led by researchers from the Indian Institute of Astrophysics (IIA), who traced an unusual X-ray flash detected on November 7, 2024, to an explosion resembling a gamma-ray burst.

FXTs are brief but highly energetic bursts of X-rays that appear suddenly in the sky and disappear within hours. Their short-lived nature has made them difficult to study since they were first discovered about a decade ago. Scientists have proposed several possible origins over the years, ranging from supernova explosions and highly magnetised neutron stars to interactions involving black holes and white dwarfs.

Global observations reveal hidden cosmic explosion

The event, known as EP241107a, was first detected by China's Einstein Probe mission, a space observatory designed to monitor rapidly changing high-energy events across the universe. To investigate further, researchers combined observations from multiple telescopes operating at different wavelengths.

A radio signal linked to the X-ray flash was detected using the Karl G. Jansky Very Large Array in New Mexico, providing an important clue about the nature of the event. Scientists also carried out follow-up observations using several Indian facilities, including the Himalayan Chandra Telescope and the GROWTH India Telescope at the Indian Astronomical Observatory in Hanle, Ladakh.

Additional observations came from the Upgraded Giant Metrewave Radio Telescope in India, the Keck Observatory in Hawaii, and the Southern Astrophysical Research Telescope in Chile. Together, these instruments allowed researchers to build a detailed picture of the explosion and its aftermath.

Evidence points to a gamma-ray burst origin

After comparing the optical and radio signatures of EP241107a with other known cosmic explosions, the team concluded that the event was most likely caused either by the collapse of a massive star or by the merger of two neutron stars.

Their analysis suggests that the explosion launched a powerful jet carrying an enormous amount of energy. According to the researchers, the kinetic energy involved was comparable to the total energy emitted by all the stars in the Milky Way over several months if it were radiated equally in every direction.

The study indicates that EP241107a belongs to a rare category of events known as "orphan afterglows." These explosions are linked to gamma-ray bursts even though no gamma rays are directly detected. Scientists believe the event may represent a lower-energy version of the gamma-ray bursts that have been observed previously.

Indian researchers play a key role

The research was led by Deepak Eappachen and Arvind Balasubramanian, postdoctoral fellows at the Indian Institute of Astrophysics. The study also involved scientists from IIT Bombay and several leading international institutions, including the California Institute of Technology, the University of North Carolina at Chapel Hill, and the Center for Astrophysics, Harvard & Smithsonian.

Researchers believe the findings will help improve our understanding of the extreme physical processes that power some of the universe's most violent explosions and may offer fresh insights into how these rare transient events are formed.