GUWAHATI: Indian Institute of Technology Guwahati and Indian Space Research Organisation (ISRO) researchers have made a groundbreaking discovery while studying the first known Galactic Ultraluminous X-ray emitting pulsar, Swift J0243.6+6124.
Their collaborative research shows that the polarization of X-rays emitted by this pulsar is significantly lower than expected, challenging existing theories of emitted radiations from these astronomical bodies.
This result challenges long-held beliefs about how X-rays interact with strong magnetic fields around neutron stars.
Researchers worldwide have been investigating the nature of polarized X-ray emissions from Swift J0243.6+6124.
The ISRO and IITG scientists focused on this source during its active period in 2023, using NASA’s Imaging X-ray Polarimetry Explorer (IXPE) to detect the polarized X-rays emission for the first time.
The team’s study, conducted using data from NASA’s IXPE, NICER, and NuSTAR missions, reveals that the polarization of the pulsar’s X-rays is just 3%, far lower than expected.
The details of this research have been published in The Astrophysical Journal Letters, co-authored by Dr. Santabrata Das, Dr. Anuj Nandi, and researchers Seshadri Majumder, Rwitika Chatterjee, and Kiran M. Jayasurya.
According to Dr. Anuj Nandi of ISRO, the discovery marks a significant step in understanding the nature of these extreme cosmic objects, potentially leading to a revision of existing models of radiation behaviour.
Dr. Anuj Nandi added, “The IXPE mission’s unique capabilities made it possible to detect low polarization in X-rays from the first known Galactic ULXPs. Notably, this low polarization appears to vary with the emitted pulses.”
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Prof. Santabrata Das, Department of Physics, IIT Guwahati, said, “The discovery of lower polarization in the X-rays from Swift J0243.6+6124 is important because it makes us rethink how these stars work.”
“Neutron stars in binary systems have very strong magnetic fields that direct matter from a nearby star to their poles. This process affects the X-rays we see because the magnetic field influences how the X-rays behave. The polarization of X-rays plays a big role in this. The unexpected low means our current understanding of these magnetic fields and X-rays needs to be updated,” Das said.
This surprising result challenges current theories and raises new questions for further exploration. It also opens new opportunities for studying similar X-ray sources within our galaxy and beyond.
