Guwahati, Nov 11: Researchers from the Indian Institute of Technology-Guwahati (IIT-G) and U.R Rao Satellite Centre of Indian Space Research Organisation (ISRO), Bengaluru, have for the first time, detected polarised emissions from a black hole source that exists beyond the Milky Way galaxy through a technique called X-ray polarimetry.
The research team, led by Prof Santabrata Das from IIT-G and Dr Anuj Nandi from URSC, comprises research scholars, Seshadri Majumder (IIT Guwahati) and Ankur Kushwaha (URSC).
Highlighting the importance of the research, Prof Santabrata Das from the department of physics, IIT-G said, “X-ray polarimetry is a unique observational technique to identify where radiation comes from near black holes. LMC X-3 (a binary star system consisting of a black hole and a ‘normal’ star) emits X-rays that are 10,000 times more powerful than those from the Sun.
“When these X-rays interact with the material around black holes, specifically when they scatter, it changes the polarisation characteristics (degree and angle). This helps in understanding how matter is drawn toward black holes in the presence of intense gravitational forces,” Prof Das said.
The researchers studied LMC X-3 using the Imaging X-ray Polarimetry Explorer (IXPE), the first mission of NASA to study the polarisation of X-rays from celestial objects.
They also made use of the simultaneous broad-band coverage of the Neutron Star Interior Composition Explorer (NICER) Mission and Nuclear Spectroscopic Telescope Array (NuSTAR) Mission to constrain the spin of LMC X-3.
Speaking about this novel finding, Dr Nandi, scientist at URSC, said, “Intense gravitational fields can cause the emitted light from black holes to become polarised. Our observations indicate that LMC X-3 harbours a black hole with low rotation rate, surrounded by a slim disc structure that gives rise to the polarised emissions.”
The study has been published in the Monthly Notices of the Royal Astronomical Society: Letters and was funded by the Science and Engineering Research Board (SERB), Department of Science and Technology, India.
The findings have opened a new window to investigate and understand the nature of astrophysical black hole sources.