Evidence of magnetospheric vacuum birefringence in the polarized X-rays of a radio magnetar
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arXiv
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| Autori principali: | , , , , , , , , , , , , , , , |
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| Natura: | Preprint |
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2025
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| author | Stewart, Rachael E. Thi, Hoa Dinh Younes, George Lower, Marcus E. Baring, Matthew G. Negro, Michela Camilo, Fernando Coley, Joel B. Enoto, Teruaki Harding, Alice K. Ho, Wynn C. G. Hu, Chin-Ping Kaaret, Philip Scholz, Paul Van Kooten, Alex Wadiasingh, Zorawar |
| author_facet | Stewart, Rachael E. Thi, Hoa Dinh Younes, George Lower, Marcus E. Baring, Matthew G. Negro, Michela Camilo, Fernando Coley, Joel B. Enoto, Teruaki Harding, Alice K. Ho, Wynn C. G. Hu, Chin-Ping Kaaret, Philip Scholz, Paul Van Kooten, Alex Wadiasingh, Zorawar |
| contents | The quantum electrodynamics (QED) theory predicts that the quantum vacuum becomes birefringent in the presence of ultra-strong magnetic fields -- a fundamental effect yet to be directly observed. Magnetars, isolated neutron stars with surface fields exceeding $10^{14}$ G, provide unique astrophysical laboratories to probe this elusive prediction. Here, we report phase- and energy-resolved X-ray polarization measurements of the radio-emitting magnetar 1E 1547.0--5408 obtained with the Imaging X-ray Polarimetry Explorer (IXPE), in coordination with the Neutron Star Interior Composition Explorer (NICER) and Parkes/Murriyang radio observations. We detect a high phase-averaged polarization degree of 65% at 2 keV, where the surface thermal emission is dominant, rising to nearly 80% at certain rotational phases, and remaining at $\gtrsim40\%$ throughout the radio beam crossing. We also observe a strong decrease in polarization from 2 keV to 4 keV. Detailed atmospheric radiative transfer modeling, coupled with geometrical constraints from radio polarization, demonstrate that the observed polarization behavior cannot be consistently explained without invoking magnetospheric vacuum birefringence (VB) influences. These observational findings combined with theoretical simulations provide evidence for quantum VB naturally occurring in magnetar magnetospheres. This work marks a significant advance toward confirming this hallmark prediction of QED and lays the foundation for future tests of strong-field quantum physics using next-generation X-ray polarimeters. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_19446 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Evidence of magnetospheric vacuum birefringence in the polarized X-rays of a radio magnetar Stewart, Rachael E. Thi, Hoa Dinh Younes, George Lower, Marcus E. Baring, Matthew G. Negro, Michela Camilo, Fernando Coley, Joel B. Enoto, Teruaki Harding, Alice K. Ho, Wynn C. G. Hu, Chin-Ping Kaaret, Philip Scholz, Paul Van Kooten, Alex Wadiasingh, Zorawar High Energy Astrophysical Phenomena High Energy Physics - Experiment Quantum Physics The quantum electrodynamics (QED) theory predicts that the quantum vacuum becomes birefringent in the presence of ultra-strong magnetic fields -- a fundamental effect yet to be directly observed. Magnetars, isolated neutron stars with surface fields exceeding $10^{14}$ G, provide unique astrophysical laboratories to probe this elusive prediction. Here, we report phase- and energy-resolved X-ray polarization measurements of the radio-emitting magnetar 1E 1547.0--5408 obtained with the Imaging X-ray Polarimetry Explorer (IXPE), in coordination with the Neutron Star Interior Composition Explorer (NICER) and Parkes/Murriyang radio observations. We detect a high phase-averaged polarization degree of 65% at 2 keV, where the surface thermal emission is dominant, rising to nearly 80% at certain rotational phases, and remaining at $\gtrsim40\%$ throughout the radio beam crossing. We also observe a strong decrease in polarization from 2 keV to 4 keV. Detailed atmospheric radiative transfer modeling, coupled with geometrical constraints from radio polarization, demonstrate that the observed polarization behavior cannot be consistently explained without invoking magnetospheric vacuum birefringence (VB) influences. These observational findings combined with theoretical simulations provide evidence for quantum VB naturally occurring in magnetar magnetospheres. This work marks a significant advance toward confirming this hallmark prediction of QED and lays the foundation for future tests of strong-field quantum physics using next-generation X-ray polarimeters. |
| title | Evidence of magnetospheric vacuum birefringence in the polarized X-rays of a radio magnetar |
| topic | High Energy Astrophysical Phenomena High Energy Physics - Experiment Quantum Physics |
| url | https://arxiv.org/abs/2509.19446 |