Researchers from the Indian Institute of Technology Guwahati and the Indian Space Research Organisation (ISRO) have made a significant breakthrough in the study of Swift J0243.6+6124, the first known Galactic Ultraluminous X-ray emitting pulsar.
Their research reveals that the X-rays emitted by this pulsar have much lower polarisation than previously thought, challenging long-standing theories about radiation from such celestial bodies.
The joint study focused on Swift J0243.6+6124 during its active phase in 2023, using data from NASA's Imaging X-ray Polarimetry Explorer (IXPE), NICER, and NuSTAR missions.
For the first time, they detected polarised X-ray emissions from the pulsar and discovered that the polarisation was merely 3%, far below the expected levels.
This discovery challenges conventional views on how X-rays interact with the strong magnetic fields surrounding neutron stars.
The findings suggest that the current understanding of X-ray radiation behaviour in these extreme environments may need revision.
Co-authored by Dr. Santabrata Das from IIT Guwahati, Dr. Anuj Nandi from ISRO, and researchers Seshadri Majumder, Rwitika Chatterjee, and Kiran M. Jayasurya, the study has been published in The Astrophysical Journal Letters.
Dr. Nandi stressed on the significance of the discovery in deepening human's knowledge of extreme cosmic objects.
"The IXPE mission’s unique capabilities allowed us to detect low polarisation in X-rays from the first known Galactic ULXPs. Notably, this low polarisation appears to vary with the emitted pulses," he said.
Prof. Santabrata Das from IIT Guwahati’s Department of Physics noted that this unexpected finding compels a reevaluation of how these stars operate.
“Neutron stars in binary systems possess very strong magnetic fields that channel material from a nearby star to their poles. This affects the X-rays we observe, as the magnetic fields influence their behaviour. The lower-than-expected polarisation indicates that our current understanding of these magnetic fields and X-rays may need to be updated,” Das explained.
This surprising result raises new questions and provides fresh avenues for research into similar X-ray sources within our galaxy and beyond.
The discovery marks a substantial step forward in the study of X-ray emissions, opening up possibilities for future astronomical research.
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