Researchers at Indian Institute of Technology Guwahati in collaboration with U. R. Rao Satellite Centre, ISRO, and Haifa University, Isreal, have uncovered a mysterious X-ray signal pattern emitted from a blackhole called GRS 1915+105, located nearly 28,000 light-years from Earth. Using the data from India’s space observatory AstroSat, the researchers observed the X-ray brightness from the black hole alternated between bright and dim phases, each lasting several hundred seconds.

Researchers from across the world are working towards understanding the phenomena of black holes. While drawing gas from the outer layers of their companion stars, they produce extreme heat and emit X-rays. By studying these X-rays, scientists can learn about the environment near the black hole.

Speaking about the key findings of the research Prof. Santabrata Das, Department of Physics, IIT Guwahati, said, “We have found the first evidence of rapid X-ray flickering, repeating nearly 70 times per second (∼70 Hz), occurring during the high-brightness phases of the source. Interestingly, these fast flickers disappear during the low-brightness phases. This new understanding was made possible by AstroSat’s powerful unique observational capabilities.”

The researchers observed that the X-ray brightness from the targeted black hole alternated between two distinct phases: one bright and one dim. During the brighter phases, when the flickers are strongest, the corona becomes more compact and significantly hotter. In contrast, during the dimmer phases, it expands and cools, causing the flickers to disappear. This clear correlation points to the compact, oscillating corona as the likely source of these fast signals.

While each phase lasted several hundred seconds and repeated in a regular pattern, a rapid flickering signal appeared only during the bright phase.