Produced by: Tarun Mishra Designed by: Manoj Kumar
India’s first dedicated multi-wavelength space observatory, AstroSat, has made a remarkable finding regarding the black hole binary source Swift J1727.8-1613.
A team of astrophysicists from U R Rao Satellite Centre (URSC), IIT Guwahati, University of Mumbai, and Tata Institute of Fundamental Research (TIFR) reported this discovery in the Monthly Notices of the Royal Astronomical Society (MNRAS).
Black holes are regions in space with gravitational pull so intense that nothing, not even light, can escape. This occurs when a massive star collapses under its own gravity at the end of its life cycle.
In BH-XRB systems, a black hole and its companion star are gravitationally bound, with the black hole pulling matter from its companion to form a bright accretion disk emitting high-energy X-rays.
Swift J1727.8-1613, discovered on August 24, 2023, by the Swift/BAT, became one of the brightest sources, peaking at about 7 Crab units in X-ray emission. AstroSat observed it from September 2 to September 14, 2023.
During its observations, AstroSat discovered unusual high-energy X-ray behavior from Swift J1727.8-1613 during a rare outburst, observing a phenomenon called 'aperiodic modulation.'
This modulation caused X-rays to exhibit repeating patterns known as QPOs, observed for the first time in this system. The frequency of these QPOs varied from 1.4 to 2.6 times per second over a week.
These high-energy X-rays are produced when lower-energy light from the accretion disk around the black hole interacts with very hot electrons, leading to the observed QPOs.
QPOs are crucial for understanding black holes, providing insights into strong gravitational forces and matter behavior around black holes. The team used AstroSat’s Large Area X-ray Proportional Counter (LAXPC) and data from the NICER instrument on the ISS to study these QPOs comprehensively.