Guwahati: A team of researchers from the Indian Institute of Technology Guwahati in Assam, in collaboration with scientists from the U. R. Rao Satellite Centre (ISRO) and Haifa University, Israel, has decoded previously unexplained flickering X-ray signals from a black hole located nearly 28,000 light-years from Earth.
The black hole, designated GRS 1915 105, has long attracted scientific interest due to its unusual energy patterns. Using data from India’s space observatory AstroSat, the team observed that the black hole’s X-ray brightness alternates between bright and dim phases, each lasting several hundred seconds.
The researchers detected rapid X-ray flickers at a frequency of approximately 70 times per second (70 Hz) during the bright phases.
These signals were absent during the dim phases, revealing a clear correlation between the black hole’s brightness and the flickering activity.
The researchers associate the phenomenon with the corona, a compact, superheated region of gas surrounding the black hole.
n brighter phases, the corona becomes hotter and more compact, generating the flickers. In dimmer phases, it expands and cools, leading to the disappearance of the flickering.
“This is the first clear evidence of rapid X-ray flickering disappearing during dim phases. AstroSat’s observational capabilities made this possible,” said Prof. Santabrata Das of the Physics Department at IIT Guwahati.
The findings offer new insights into the extreme environment near a black hole, where gravitational forces are intense and temperatures reach several million degrees. The research also contributes to existing models of how black holes consume gas, emit energy, and influence their surroundings.
Dr. Anuj Nandi from URSC, ISRO, noted, “Our study provides direct evidence that these flickers originate from changes in the corona itself. It is a significant step toward understanding black hole physics.”
The international study, co-authored by Prof. Das, his research scholar Seshadri Majumder, Dr. Nandi of ISRO, and Dr. Sreehari Harikesh of Haifa University, has been published in the Monthly Notices of the Royal Astronomical Society (MNRAS).
Researchers believe that such studies not only enhance understanding of black holes but also shed light on how these objects may influence galaxy evolution.
