Observations of the Magnetar 1E 2259+586 with NuSTAR

We present new spectral and temporal observations of the magnetar 1E 2259+586 located in the supernova remnant CTB 109. Our analysis covers the energy range from 0.5-79 keV and is based on data acquired simultaneously with the Nuclear Spectroscopic Telescope Array (NuSTAR) and Swift. Double-peaked pulse profiles in various energy bands are shown and we compare them to previously published RXTE results. With NuSTAR, pulsations above 20 keV are observed for the first time and we report evidence that one of the pulses in the double-peaked pulse profile shifts position with energy. We found the pulsed fraction of the magnetar increases strongly with energy and our spectral analysis reveals that the soft X-ray spectrum is well characterized by an absorbed double-blackbody or blackbody plus power-law model in agreement with previous reports. Our new hard X-ray data, however, suggests that an additional component, such as a power-law, is needed to describe the NuSTAR and Swift spectrum. We also fit the data with the recently developed coronal outflow model by Beloborodov for hard X-ray emission from magnetars and show that the outflow from a ring on the magnetar surface is statistically preferred over outflow from a polar cap.Part of this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 (LLNL-ABS-654716).