A multi-institutional team including IIT Guwahati, ISRO’s UR Rao Satellite Centre (URSC), and Haifa University (Israel) has uncovered rapid X-ray flickering signals from the black hole GRS 1915+105 using AstroSat data. The study shows these signals arise from changes in the black hole’s corona during bright phases.

The black hole, nearly 28,000 light-years from Earth, exhibits alternating bright and dim phases, each lasting several hundred seconds. During the bright phases, scientists observed rapid X-ray flickering at about 70 times per second (70 Hz)—a phenomenon absent in the dimmer phases.

First Evidence of Rapid X-Ray Flickering

Professor Santabrata Das of IIT Guwahati explained:

“We have found the first evidence of rapid X-ray flickering, repeating nearly 70 times per second, occurring during the high-brightness phases. Interestingly, these fast flickers disappear during the low-brightness phases. This new understanding was made possible by AstroSat’s unique observational capabilities.”

The findings indicate that during bright phases, the corona—the hot, ionized region around the black hole—contracts and heats up, producing flickers. In contrast, during dim phases, the corona expands and cools, causing the flickers to vanish.

Significance for Black Hole Studies

Dr Anuj Nandi from ISRO noted that the study provides direct evidence linking X-ray flickering to modulations in the corona. This not only improves scientific understanding of extreme conditions near black holes but also sheds light on how black holes may influence galaxy evolution by regulating energy and matter flow.

The study, co-authored by Prof. Das, research scholar Seshadri Majumder, Dr. Nandi, and Dr. Sreehari Harikesh of Haifa University, has been published in the Monthly Notices of the Royal Astronomical Society (MNRAS).

Image Source: Google | Image Credit: Respective Owner