DEEP NuSTAR and SWIFT MONITORING OBSERVATIONS of the MAGNETAR 1E 1841-045

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 T ₉₀ ≲ 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 phase-resolved 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, , 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.