BROAD RELATIVISTIC IRON EMISSION LINE OBSERVED IN SAX J1808.4-3658

During the 2008 September-October outburst of the accreting millisecond pulsar SAX J1808.4-3658, the source was observed by both Suzaku and XMM-Newton approximately 1 day apart. Spectral analysis reveals a broad relativistic Fe K alpha emission line which is present in both data sets, as has recently been reported for other neutron star low-mass X-ray binaries. The properties of the Fe K line observed during each observation are very similar. From modeling the Fe line, we determine the inner accretion disk radius to be 13.2 +/- 2.5 GM c(-2). The inner disk radius measured from the Fe K line suggests that the accretion disk is not very receded in the hard state. If the inner disk ( as measured by the Fe line) is truncated at the magnetospheric radius this implies a magnetic field strength of similar to 3 x 10(8) G at the magnetic poles, consistent with other independent estimates.