5 days ago
AstroSat helps decode mysterious black hole flickers: ISRO
Bengaluru, Jul 25 (PTI) Indian scientists are employing AstroSat, the country's first dedicated multi-wavelength space observatory, to understand the complex behaviour exhibited by the black hole system GRS 1915+105, the ISRO said.
The study conducted by researchers from ISRO, IIT Guwahati, and the University of Haifa (Israel), has revealed that the X-ray brightness from the black hole fluctuates rapidly, alternating between low brightness (dip) and high-brightness (non-dip) phases, each lasting a few hundred seconds.
During these high-brightness phases, the team observed rapid X-ray flickers about 70 times per second, which is known as Quasi-Periodic Oscillations (QPOs).
The research team uncovered that these rapid QPOs are intimately connected to a 'super-heated' cloud of energetic plasma surrounding the black hole, known as Corona.
During the bright high-energy phases when QPOs are strongest, the corona becomes more compact and significantly hotter. Conversely, in the dimmer 'dip' phases, the corona expands and cools, causing the flickers to vanish. This pattern suggests that the compact oscillating corona seems to be the origin of these fast QPO signals, ISRO noted in a statement.
This discovery was made using AstroSat's Large Area X-ray Proportional Counter (LAXPC) and Soft X-ray Telescope (SXT).
'These findings help scientists understand what happens in the vicinity of a black hole, where gravity is incredibly strong and conditions are extreme," ISRO said.
GRS 1915+105, with a mass about 12 times that of a Sun, is located about 28,000 light-years away.
The study has been published in the Monthly Notices of the Royal Astronomical Society and co-authored by Anuj Nandi (ISRO), Santabrata Das and Seshadri Majumder (IIT Guwahati), and Sreehari H (University of Haifa). PTI GMS GMS ROH
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First Published:
July 25, 2025, 22:15 IST
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