Deep NuSTAR and Swift monitoring observations of the magnetar 1E 1841-045

Hongjun An, Robert F. Archibald, Romain Hascoët, Victoria M. Kaspi, Andrei M. Beloborodov, Anne M. Archibald, Andy Beardmore, Steven E. Boggs, Finn Erland Christensen, William W. Craig

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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 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 αmag the twisted magnetic flux, 2.5 × 1026 G cm2, and the power released in the twisted magnetosphere, = 6 × 1036 erg s-1. Assuming this model for the hard-X-ray spectrum, the soft-X-ray component is well fit by a two-black body 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.
Original languageEnglish
Article number93
JournalAstrophysical Journal
Volume807
Issue number1
Number of pages16
ISSN0004-637X
DOIs
Publication statusPublished - 2015

Keywords

  • Pulsars: individual (1E 1841–045)
  • Stars: magnetars
  • Stars: neutron
  • X-rays: bursts

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