Joint XMM-NuSTAR Observations of 1E 1048.1-5937

Hard Xray emission from magnetars was discovered by INTEGRAL, and generallycomprises more luminosity than is seen below 10 keV. However, the origin of thispowerful hard Xray emission is unknown. NuSTAR is a recently launched NASAmission, the first focusing hard Xray telescope. Operating in the 379 keVband, it has sensitivity virgul100x better than previous telescopes in this energyrange. NuSTAR is a superb instrument for studying the hard Xray emission frommagnetars. Here we propose simultaneous XMM and NuSTAR observations of magnetar1E 1048.15937, to obtain highquality broadband Xray spectrum to test aproposed correlation between spectral turnover and magnetic field, and forcomparison with the predictions of a new model for magnetar hard Xray emission. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]