iit-guwahati-isro-decode-x-ray-flickers-from-distant-black-hole

An international team of scientists led by IIT Guwahati has identified a rare pattern of flickering X-ray signals from a distant black hole, shedding new light on the behaviour of matter in extreme gravitational conditions. The discovery was made using data from the Indian space observatory, AstroSat, and involved collaboration with the UR Rao Satellite Centre, ISRO, and Haifa University in Israel.

 

The team observed that the black hole, situated nearly 28,000 light-years away, alternated between bright and dim phases, each lasting several hundred seconds. Remarkably, fast X-ray flickers repeating nearly 70 times per second were detected only during the high-brightness phases.

 

"We have found the first evidence of rapid X-ray flickering, repeating nearly 70 times per second, 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," said Santabrata Das, Professor at the Department of Physics, IIT Guwahati

 

Researchers noted that during the brighter phases the corona around the black hole becomes more compact and hotter, resulting in strong flickers. Conversely, during the dimmer phases, the corona expands and cools, and the flickers disappear.

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"This clear correlation points to the compact, oscillating corona as the likely source of these fast signals," Das added. He said the findings revealed that the corona around a black hole is not a static structure and changes in size and temperature depending on the flow of gases.

 

Das noted that the research offers insight into extreme gravitational and thermal conditions near the edge of a black hole and helps refine existing models of black hole growth and energy emission. The work, published in the Monthly Notices of the Royal Astronomical Society, also provides clues to how black holes influence the evolution of their host galaxies.

 

"Our study provides direct evidence for the origin of X-ray flickering. We have found that this flickering is linked to modulations in the corona surrounding the black hole," said Anuj Nandi of the UR Rao Satellite Centre, ISRO.