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

Rachael Stewart; George A. Younes; Alice K. Harding; Zorawar Wadiasingh; Matthew G. Baring; Michela Negro; Tod E. Strohmayer; Wynn C. G. Ho; Mason Ng; Zaven Arzoumanian; Hoa Dinh Thi; Niccolò Di Lalla; Teruaki Enoto; Keith Gendreau; Chin-Ping Hu; Alex van Kooten; Chryssa Kouveliotou; Alexander McEwen

doi:10.3847/2041-8213/adbffa

The Astrophysical Journal Letters (Jan 2025)

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

Rachael Stewart,
George A. Younes,
Alice K. Harding,
Zorawar Wadiasingh,
Matthew G. Baring,
Michela Negro,
Tod E. Strohmayer,
Wynn C. G. Ho,
Mason Ng,
Zaven Arzoumanian,
Hoa Dinh Thi,
Niccolò Di Lalla,
Teruaki Enoto,
Keith Gendreau,
Chin-Ping Hu,
Alex van Kooten,
Chryssa Kouveliotou,
Alexander McEwen

Affiliations

Rachael Stewart: ORCiD; Department of Physics, The George Washington University , Washington, DC 20052, USA
George A. Younes: ORCiD; Astrophysics Science Division, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA; Center for Space Sciences and Technology, University of Maryland , Baltimore County, Baltimore, MD 21250, USA
Alice K. Harding: ORCiD; Theoretical Division, Los Alamos National Laboratory , Los Alamos, NM 87545, USA
Zorawar Wadiasingh: ORCiD; Astrophysics Science Division, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA; Department of Astronomy, University of Maryland , College Park, MD 20742, USA; Center for Research and Exploration in Space Science and Technology , NASA/GSFC, Greenbelt, MD 20771, USA
Matthew G. Baring: ORCiD; Department of Physics and Astronomy—MS 108, Rice University , 6100 Main Street, Houston, TX 77251-1892, USA
Michela Negro: ORCiD; Department of Physics & Astronomy, Louisiana State University , Baton Rouge, LA 70803, USA
Tod E. Strohmayer: ORCiD; Astrophysics Science Division, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA
Wynn C. G. Ho: ORCiD; Department of Physics and Astronomy, Haverford College , 370 Lancaster Avenue, Haverford, PA 19041, USA
Mason Ng: ORCiD; Department of Physics, McGill University , 3600 rue University, Montréal, QC H3A 2T8, Canada; Trottier Space Institute, McGill University , 3550 rue University, Montréal, QC H3A 2A7, Canada
Zaven Arzoumanian: ORCiD; Astrophysics Science Division, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA
Hoa Dinh Thi: ORCiD; Department of Physics and Astronomy—MS 108, Rice University , 6100 Main Street, Houston, TX 77251-1892, USA
Niccolò Di Lalla: ORCiD; W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University , Stanford, CA 94305, USA
Teruaki Enoto: ORCiD; RIKEN Cluster for Pioneering Research , 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
Keith Gendreau: ORCiD; Astrophysics Science Division, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA
Chin-Ping Hu: ORCiD; Department of Physics, National Changhua University of Education , Changhua 50007, Taiwan
Alex van Kooten: ORCiD; Department of Physics, The George Washington University , Washington, DC 20052, USA
Chryssa Kouveliotou: ORCiD; Department of Physics, The George Washington University , Washington, DC 20052, USA
Alexander McEwen: ORCiD; Center for Space Sciences and Technology, University of Maryland , Baltimore County, Baltimore, MD 21250, USA

DOI: https://doi.org/10.3847/2041-8213/adbffa
Journal volume & issue: Vol. 985, no. 2
p. L35

Abstract

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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.

Published in The Astrophysical Journal Letters

ISSN: 2041-8205 (Print); 2041-8213 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Astronomy: Astrophysics
Website: https://iopscience.iop.org/journal/2041-8205

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