Stewart, RachaelYounes, GeorgeHarding, AliceWadiasingh, ZorawarBaring, MatthewNegro, MichelaStrohmayer, TodHo, WynnNg, MasonArzoumanian, ZavenThi, Hoa DinhLalla, Niccolo' DiEnoto, TeruakiGendreau, KeithHu, Chin-PingKooten, Alex vanKouveliotou, ChryssaMcEwen, Alexander2025-01-312025-01-312024-12-20https://doi.org/10.48550/arXiv.2412.16036http://hdl.handle.net/11603/37552We report on IXPE and NuSTAR observations that began forty days following the onset of the 2024 outburst of the magnetar 1E 1841-045, marking the first ever IXPE observation of a magnetar in an enhanced state. Our spectropolarimetric analysis indicates that a non-thermal double power-law (PL) spectral model can fit the phase-averaged intensity data well, with the soft and hard components dominating below and above around 5 keV, respectively. We find that the soft PL exhibits a polarization degree (PD) of about 20% while the hard X-ray PL displays a PD of about 50%; both components have a polarization angle (PA) compatible with 0 degree. These results are supported through model-independent polarization analysis which shows an increasing PD from about 15% to 70% in the 2-3 keV and 6-8 keV ranges, respectively, while the PA remains consistent with 0 degree. We find marginal evidence for variability in the polarization properties with pulse phase, namely a higher PD at spin phases coinciding with the peak in the hard X-ray pulse. We compare the hard X-ray PL to the expectation from direct resonant inverse Compton scattering (RICS) and secondary pair cascade synchrotron radiation from primary high-energy RICS photons, finding that both can provide reasonable spectropolarimetric agreement with the data, yet, the latter more naturally. Finally, we suggest that the soft power law X-ray component may be emission emanating from a Comptonized corona in the inner magnetosphere.14 pagesen-USThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.Public Domainhttps://creativecommons.org/publicdomain/mark/1.0/Astrophysics - High Energy Astrophysical PhenomenaText