IUCAA Brochure 2024

as predicted by Einstein's general theory of relativity. They have also found the first evidence for a state transition in a changing-look active galaxy where the standard disk changes its structure and forms a warmmedium producing soft X-ray excess emission. As part of an international collaboration, IUCAA researchers observed with AstroSat's Soft X-ray Telescope, and helped unravel a mysterious super bright flash with fast variability, to be a tidal disruption event in which an SMBH in a distant galaxy captured a star and produced a relativistic jet which pointed towards the earth, which producedmore light than a 1000 trillionSuns. In a study of a transient black hole X-ray binary MAXI J1820+070, IUCAA scientists find changes in the inner radius of the accretion disk associated with changes in the structure of and emission from the hot Corona. This study further revealed a captivating connection between the X-ray emission from the inner regions near the black hole and optical/UV emission from the outer region of the accretion disk. In another research data fromAstroSat's CadmiumZinc Telluride Imager (CZTI), reported around 24% polarised high energy X-rays from the black hole X-ray binary Cygnus X-1. This is much higher than the expected less than 10%, thus hinting that the mechanism of X-ray emission (more energetic than 200 keV) is from the jet, possibly synchrotron radiation in an ordered magnetic field. Moreover, the CZTI detected high X-ray polarisation only in the state that exhibits strong radio emission from the jet. For the first time, therefore, one can confirm the direct connection of the hard X-ray emission to the relativistic jet.