The anomalous X-ray pulsar 1E 1048.1-5937: Phase resolved spectroscopy with the XMM-Newton satellite

We report on an observation of the anomalous X–ray pulsar 1E 1048.1–5937 performed with the XMM-Newton satellite. The phase averaged spectrum of 1E 1048.1–5937 is well described by the sum of a power law with photon index ~2.9 and a blackbody with temperature ~0.6 keV, without evidence for significant absorption or emission lines. The above spectral parameters do not vary during the phases corresponding to the broad pulse, while the off pulse emission shows a different spectrum characterized by a soft excess at energies below ~1.5 keV. The XMM-Newton observation and a re-analysis of archival BeppoSAX data show that the spectral parameters and flux of 1E 1048.1–5937 did not change significantly during observations spanning the last four years. All the data are consistent with a 2–10 keV luminosity varying in the range ~(5–7)$\times$10 33 erg s -1 (for a distance of 3 kpc).