Indian astronomers have played a key role in unraveling the mystery behind a rare cosmic X-ray flash that appeared suddenly and vanished within hours. The findings provide fresh insights into some of the most violent events in the universe.
Discovery of the Fast X-ray Transient
An international team led by researchers from the Indian Institute of Astrophysics (IIA) traced the origin of a rare Fast X-ray Transient (FXT) named EP241107a. This fleeting burst of X-rays was detected on November 7, 2024, by China's Einstein Probe mission. The study sheds light on these enigmatic phenomena and may help solve a long-standing astronomical puzzle.
What Are Fast X-ray Transients?
FXTs are among the newest and most mysterious phenomena in the night sky. These powerful flashes appear without warning, last from minutes to hours, and then disappear. Their short-lived nature has made it difficult for astronomers to determine their causes.
Global Observing Campaign
To investigate EP241107a, scientists launched a global campaign using some of the world's most advanced telescopes. The breakthrough came when the team identified a radio counterpart to the X-ray flash using the Karl G. Jansky Very Large Array in New Mexico. This provided a crucial clue about the event's origin.
Indian Facilities Used
Researchers relied on several major Indian facilities, including the Himalayan Chandra Telescope, the GROWTH India Telescope in Ladakh, and the Upgraded Giant Metrewave Radio Telescope. Additional observations were conducted using the Keck Observatory in Hawaii and the Southern Astrophysical Research Telescope in Chile.
Origin of the Flash
After analyzing optical and radio data, along with the host galaxy, the team concluded that EP241107a was likely linked to a gamma-ray burst-like explosion. This could have resulted from the collapse of a massive star or the merger of two neutron stars. The explosion launched an extraordinarily powerful jet of matter and energy, carrying kinetic energy comparable to the total energy emitted by all stars in the Milky Way over several months.
Orphan Afterglow Discovery
Intriguingly, no gamma rays were directly detected from the event. Yet, its afterglow strongly suggests a gamma-ray burst origin, making EP241107a one of the clearest examples of an 'orphan afterglow'—the lingering signature of a cosmic explosion whose initial gamma-ray flash went unseen.
The researchers believe the event may represent a previously overlooked, lower-energy member of the gamma-ray burst family, opening a new window into understanding how these colossal explosions occur across the universe.
Publication and Collaborators
The study was published in the Monthly Notices of the Royal Astronomical Society. It involved researchers from the Indian Institute of Astrophysics, IIT Bombay, the California Institute of Technology, the University of North Carolina at Chapel Hill, and the Center for Astrophysics, Harvard & Smithsonian.
