IIT Guwahati, ISRO researchers detect X-Ray polarization from black hole source outside our Milky Way Galaxy

NEW DELHI: Indian Institute of Technology Guwahati (IIT Guwahati) researchers, Indian Space Research Organisation (ISRO) Bengaluru, and UR Rao Satellite Centre have detected polarized emissions from a black hole source.

The researchers detected the emission that exists beyond our Milky Way Galaxy through a technique called X-ray polarimetry.

Large Magellanic Cloud X-3 (LMC X3) is a binary star system consisting of a black hole and a ‘normal’ star that is much hotter, bigger, and more massive than the Sun. It is located in a satellite galaxy of our Milky Way, nearly 200,000 light-years away from Earth.

The research team is led by Santabrata Das from IIT Guwahati and Anuj Nandi from URSC Bangalore, and research scholars Seshadri Majumder from IIT Guwahati) and Ankur Kushwaha from URSC.

These findings will help decipher, investigate and understand the nature of astrophysical black hole sources.

“Since its discovery in 1971, it has been observed by various satellites. However, there has been a gap in understanding the polarization properties of X-rays emitted by highly energetic objects like stellar mass black holes in the universe,” the institute said.

LMC X3 a binary star system

Santabrata Das, professor of department of physics, IIT Guwahati, said: “X-ray polarimetry is a unique observational technique to identify where radiation comes from near black holes. LMC X-3 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 polarization characteristics, i.e. degree and angle. This helps in understanding how matter is drawn toward black holes in the presence of intense gravitational forces.”

The researchers studied LMC X-3 using The Imaging X-ray Polarimetry Explorer (IXPE), the first mission of NASA to study the polarization of X-rays from celestial objects.

The researchers and scientists also made use of the simultaneous broad-band coverage of Neutron Star Interior Composition Explorer (NICER) Mission and Nuclear Spectroscopic Telescope Array (NuSTAR) Mission to constrain the spin of LMC X-3.

IIT Guwahati and ISRO researchers (Image: Official)

Speaking about the finding, Anuj Nandi, scientist at UR Rao Satellite Centre (URSC), ISRO Bangalore, said: “Intense gravitational fields can cause the emitted light from black holes to become polarized. Our observations indicate that LMC X-3 likely harbours a black hole with low rotation rate, surrounded by a slim disc structure that gives rise to the polarized 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.