X-Ray Polarization of the Magnetar 1E 1841−045

Abstract We report on IXPE and NuSTAR observations beginning 40 days after the 2024 outburst onset of magnetar 1E 1841−045, marking the first IXPE observation of a magnetar in an enhanced state. Our spectropolarimetric analysis indicates that both a blackbody (BB) plus double power-law (PL) and a double blackbody plus power-law spectral model fit the phase-averaged intensity data well, with a hard PL tail (Γ = 1.19 and 1.35, respectively) dominating above ≈5 keV. For the former model, we find the soft PL (the dominant component at soft energies) exhibits a polarization degree (PD) of ≈30% while the hard PL displays a PD of ≈40%. Similarly, the cool BB of the 2BB+PL model possesses a PD of ≈15% and a hard PL PD of ≈57%. For both models, each component has a polarization angle (PA) compatible with celestial north. Model-independent polarization analysis supports these results, wherein the PD increases from ≈15% to ≈70% in the 2–3 keV and 6–8 keV ranges, respectively, while the PA remains nearly constant. We find marginal evidence for phase-dependent variability of the polarization properties, namely a higher PD at phases coinciding with the hard X-ray pulse peak. We compare the hard X-ray PL to the expectation from resonant inverse Compton scattering (RICS) and secondary pair cascade synchrotron radiation from primary high-energy RICS photons; both present reasonable spectropolarimetric agreement with the data, albeit the latter does so more naturally. We suggest that the soft PL X-ray component may originate from a Comptonized corona in the inner magnetosphere.

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Publication Details

Journal
The Astrophysical Journal Letters
Published
2025-05-28
DOI
https://doi.org/10.3847/2041-8213/adbffa
Citations
9
Primary Topic
Pulsars and Gravitational Waves Research
Type
article
Field-Weighted Citation Impact
10.39

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article

X-Ray Polarization of the Magnetar 1E 1841−045

Wynn C. G. Ho, Niccolò Di Lalla, George Younes, Alex Van Kooten et al.
9 citations
The Astrophysical Journal Letters
Pulsars and Gravitational Waves Research
10.39
article

X-Ray Polarization of the Magnetar 1E 1841−045

Wynn C. G. Ho, Niccolò Di Lalla, George Younes, Alex Van Kooten, C. Kouveliotou, Alexander McEwen, R. J. Stewart, Hoa Dinh Thi, Zorawar Wadiasingh, Teruaki Enoto, Mason Ng, Michela Negro, A. K. Harding, Tod E. Strohmayer, Zaven Arzoumanian, Keith C. Gendreau, Chin‐Ping Hu, Matthew G. Baring
article en
9 citations

Abstract

Abstract We report on IXPE and NuSTAR observations beginning 40 days after the 2024 outburst onset of magnetar 1E 1841−045, marking the first IXPE observation of a magnetar in an enhanced state. Our spectropolarimetric analysis indicates that both a blackbody (BB) plus double power-law (PL) and a double blackbody plus power-law spectral model fit the phase-averaged intensity data well, with a hard PL tail (Γ = 1.19 and 1.35, respectively) dominating above ≈5 keV. For the former model, we find the soft PL (the dominant component at soft energies) exhibits a polarization degree (PD) of ≈30% while the hard PL displays a PD of ≈40%. Similarly, the cool BB of the 2BB+PL model possesses a PD of ≈15% and a hard PL PD of ≈57%. For both models, each component has a polarization angle (PA) compatible with celestial north. Model-independent polarization analysis supports these results, wherein the PD increases from ≈15% to ≈70% in the 2–3 keV and 6–8 keV ranges, respectively, while the PA remains nearly constant. We find marginal evidence for phase-dependent variability of the polarization properties, namely a higher PD at phases coinciding with the hard X-ray pulse peak. We compare the hard X-ray PL to the expectation from resonant inverse Compton scattering (RICS) and secondary pair cascade synchrotron radiation from primary high-energy RICS photons; both present reasonable spectropolarimetric agreement with the data, albeit the latter does so more naturally. We suggest that the soft PL X-ray component may originate from a Comptonized corona in the inner magnetosphere.

The Astrophysical Journal LettersVol. 985(2)
Louisiana State University (US), Goddard Space Flight Center (US), Los Alamos National Laboratory (US), Haverford College (US), George Washington University (US), SLAC National Accelerator Laboratory (US), Kavli Institute for Particle Astrophysics and Cosmology (US), Pioneer (Japan) (JP), RIKEN (JP), Deleted Institution, McGill University (CA), University of Maryland, College Park (US), National Changhua University of Education (TW), Rice University (US), University of Maryland, Baltimore County (US), Stanford University (US)
National Aeronautics and Space Administration
Openalex Percentile: Top 2%
Pulsars and Gravitational Waves Research
10.39
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