Researchers at IIT Guwahati, in collaboration with ISRO’s UR Rao Satellite Centre and Israel’s University of Haifa, have discovered a mysterious X-ray signal pattern from the black hole GRS 1915+105, located about 28,000 light-years away from Earth. Using data from India’s space observatory AstroSat, the team observed that the X-ray glow from the black hole alternates between bright and dim phases, each lasting several hundred seconds. This unusual pattern has intrigued scientists worldwide as they try to understand the behavior of black holes.
Fast X-Ray Flickers Revealed
Professor Santabrata Das of IIT Guwahati stated that for the first time, researchers have detected rapid X-ray flickers repeating around 70 times per second during high-luminosity phases. Interestingly, these fast flickers disappear when the black hole enters its dim phase. According to Prof Das, the unique observational capabilities of AstroSat made this discovery possible, giving scientists a new tool to study black holes and the extreme environments around them.
Dense and Oscillating Corona Explains the Signals
The research revealed that during the bright phase, the corona around the black hole becomes denser and hotter, causing the fast flickering. In the dim phase, the corona expands and cools, making the flickering disappear. This oscillating corona is now considered the likely source of these signals. Each bright and dim phase lasts several hundred seconds, repeating in a regular pattern. This shows that the corona around black holes is dynamic and constantly changing its structure and energy according to the flow of gases into the black hole.
Implications for Black Hole Understanding
These findings offer deeper insights into the extreme gravitational forces and high temperatures present at the edge of a black hole. Prof Das explained that this research helps improve models of black hole evolution, energy emission, and the influence of black holes on their surrounding galaxies. Understanding X-ray flickering also allows scientists to study how black holes impact the growth and development of entire galaxies, revealing more about these mysterious cosmic entities.
Collaborative Global Effort and Publication
Dr. Anuj Nandi of ISRO’s URSC highlighted that the study provides direct evidence linking X-ray flickering to changes in the corona. The research team includes Prof Das and his student Seshadri Majumdar from IIT Guwahati, Dr. Nandi, and Dr. Srihari Harikesh from the University of Haifa. Their work has been published in the journal Monthly Notices of the Royal Astronomical Society, marking a significant step in black hole research and providing new opportunities for future studies of high-energy cosmic phenomena.
