The X-ray polarimetry method used by Indian scientists has opened up new dimensions to investigate and understand the nature of astrophysical black hole sources.
In a major breakthrough for space science, four researchers from the Indian Space Research Organisation (ISRO) and the Indian Institute of Technology Guwahati (IIT Guwahati) for the first time in 52 years, have detected polarized emissions from a black hole source that exists beyond our Milky Way Galaxy using a technique called X-ray polarimetry.
This feat has been achieved for the first time since the discovery in 1971 of the Large Magellanic Cloud X-3 (LMC X3) star system which is binary in nature and consists of a black hole and a ‘normal’ star that is much hotter, bigger, and more massive than the Sun.
For over half a century the star system was observed by many satellites but 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 LMC X3 is located in a satellite galaxy of our Milky Way, nearly 200,000 light-years away from Earth.
The X-ray polarimetry method used by Indian scientists has opened up new dimensions to investigate and understand the nature of astrophysical black hole sources. 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. 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.
Reflecting on the importance of this research, Professor Santabrata Das, 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, that is degree and angle.” He added that this helps in understanding how matter is drawn toward black holes in the presence of intense gravitational forces.”
Dr Anuj Nandi, Scientist, UR Rao Satellite Centre (URSC), ISRO, explained that the intense gravitational fields can cause the emitted light from black holes to become polarized. “Our observations indicate that LMC X-3 likely harbors a black hole with a low rotation rate, surrounded by a slim disc structure that gives rise to the polarized emissions,” he added.
The study was 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 research team was led by Santabrata Das from IIT Guwahati and Nandi from URSC, including research scholars, Seshadri Majumder (IIT Guwahati), and Ankur Kushwaha (URSC).
source/content: newindianexpress.com (headline edited)