Phase Resolved Observations of Magnetar 4U 0142+61 with NuSTAR

We report ongoing spectral and temporal analysis of new 167 ks, 3-79 keV NuSTAR observations of magnetar 4U 0142+61. With contemporaneous Swift-XRT observations, the low energy phase-averaged spectra are well fit by T_eff = 0.461±0.006 keV blackbody and a soft (Γ≈3.85) power law and the high-energy spectra are well explained by a hard power law (Γ≈0.35±0.04). We detect pulsations at all energies in the Swift-XRT and NuSTAR observations. The fractional RMS variation in the 3-79 keV band is 14%. We detect increasing fractional RMS variation as a function of energy (9% at 3-10 keV; 17% at 10-20 keV; 20% at 20-35 keV). The pulse morphology changes from single peaked at low energies to a double peaked structure at ~35 keV. We fit the X-ray data using the electron-positron outflow model developed by Beloborodov for explaining magnetar hard X-ray spectra.