IIT Guwahati and Multi-Institutional Team Reveals New Discoveries in Black Hole Binary Systems

A multi-institutional team, including researchers from IIT Guwahati, has discovered a black hole binary system named Swift J1727.8-1613 using data from AstroSat. Know details here

The Indian Institute of Technology (IIT) Guwahati and a multi-institutional research team including U. R. Rao Satellite Centre, ISRO, University of Mumbai, and Tata Institute of Fundamental Research have studied a newly discovered black hole binary system called Swift J1727.8-1613. This study utilised data collected from AstroSat, India's first dedicated space astronomy observatory, which orbits the Earth.

AstroSat is equipped with instruments capable of observing the universe in multi-wavelengths, including X-rays, making it ideal for studying high-energy phenomena such as black hole binaries. The team has discovered intriguing X-ray characteristics that can potentially provide insights into the nature of black holes.

Speaking about the research, Prof. Santabrata Das, Department of Physics, IIT Guwahati, said, “QPOs are indispensable for investigating mysterious black hole systems. By examining the periodic variations of X-ray photons at high energies (around 100 keV), QPOs help decode the footprints of a black hole’s strong gravity. This aids in understanding their fundamental properties and the dynamics of how the black hole attracts matter from the neighboring environment.”

The researchers observed Quasi-periodic Oscillations (QPOs) in the X-ray light emitted by the accretion disk of Swift J1727.8-1613. QPOs are fluctuations in X-ray light from an astronomical object at specific frequencies. Notably, the frequency of these QPOs shifted from 1.4 to 2.6 times per second over just seven days. This frequency change was detected in extraordinarily hot and extremely high-energy X-rays, reaching temperatures around a billion degrees.

The implications of this discovery are profound. QPOs can aid astronomers in studying the inner regions of accretion disks and determining the masses and spin periods of black holes. They also provide a means to test Einstein's theory of general relativity, which describes gravity as a geometric property of space and time. According to this theory, massive objects such as black holes and neutron stars warp the fabric of spacetime around them. This curvature dictates the paths that accreting matter follows, which we perceive as gravitational attraction.

Highlighting the impact of this research finding, Dr. Anuj Nandi, U R Rao Satellite Centre, ISRO, added, “Unique capabilities of AstroSat, namely the high time resolution and large X-ray photon collecting area, made the discovery of evolving QPO frequency in high energy X-rays possible. These high-energy X-rays are generated when low-energy photons interact with hot material from inner disk around black holes via Compton scattering process. AstroSat observations distinctly confirm that Swift J1727.8−1613 was in a accretion state dominated by Comptonized emissions that manifest aperiodic modulation, resulting in observed QPO features.”

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