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Published July 2, 2015 | Submitted + Published
Journal Article Open

Deep NuSTAR and Swift Monitoring Observations of the Magnetar 1E 1841-045

Abstract

We report on a 350 ks NuSTAR observation of the magnetar 1E 1841–045 taken in 2013 September. During the observation, NuSTAR detected six bursts of short duration, with T90 ≤ 1 s. An elevated level of emission tail is detected after the brightest burst, persisting for ∼1 ks. The emission showed a power-law decay with a temporal index of 0.5 before returning to the persistent emission level. The long observation also provided detailed phaseresolved spectra of the persistent X-ray emission of the source. By comparing the persistent spectrum with that previously reported, we find that the source hard-band emission has been stable for over approximately 10 yr. The persistent hard-X-ray emission is well fitted by a coronal outflow model, where e^± pairs in the magnetosphere upscatter thermal X-rays. Our fit of phase-resolved spectra allowed us to estimate the angle between the rotational and magnetic dipole axes of the magnetar, amag = 0.25, the twisted magnetic flux, 2.5 × 10^(26) G cm^2, and the power released in the twisted magnetosphere, L_j = 6 × 10^(36) erg s^(−1). Assuming this model for the hard-X-ray spectrum, the soft-X-ray component is well fit by a two-blackbody model, with the hotter blackbody consistent with the footprint of the twisted magnetic field lines on the star. We also report on the 3 yr Swift monitoring observations obtained since 2011 July. The soft-X-ray spectrum remained stable during this period, and the timing behavior was noisy, with large timing residuals.

Additional Information

© 2015. The American Astronomical Society. Received 2015 January 28, accepted for publication 2015 May 13 Published 2015 July 2. This work was supported under NASA Contract No. NNG08FD60C, and made use of data from the NuSTAR mission, a project led by the California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by the National Aeronautics and Space Administration. We thank the NuSTAR Operations, Software and Calibration teams for support with the execution and analysis of these observations. This research has made use of the NuSTAR Data Analysis Software (NuSTARDAS) jointly developed by the ASI Science Data Center (ASDC, Italy) and the California Institute of Technology (USA). H.A. acknowledges supports provided by the NASA sponsored Fermi Contract NAS5-00147 and by Kavli Institute for Particle Astrophysics and Cosmology. V.M.K. acknowledges support from an NSERC Discovery Grant and Accelerator Supplement, the FQRNT Centre de Recherche Astrophysique du Québec, an R. Howard Webster Foundation Fellowship from the Canadian Institute for Advanced Research (CIFAR), the Canada Research Chairs Program and the Lorne Trottier Chair in Astrophysics and Cosmology. A.M.B. acknowledges the support by NASA grant NNX13AI34G.

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Published - 0004-637X_807_1_93.pdf

Submitted - 1505.03570v2.pdf

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August 20, 2023
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