  We report on the results of a 50ks BeppoSAX observation of 1RXS
J170849-400910, one of the five (plus a candidate) known anomalous X-ray
pulsars. The BeppoSAX data are consistent with a power-law plus blackbody
spectral decomposition, making 1RXS J170849-400910 the fourth source of this
class for which such a spectral decomposition was found. The inferred power-law
slope and blackbody temperature are Gamma~2.6 and kT_BB~0.46keV, respectively.
We found significant energy-dependence of the pulse profile, a remarkable
feature for an AXP. By using the power-law plus blackbody decomposition we
detected a significant variation in at least one spectral parameter, the
power-law photon index, as a function of the pulse phase. This is the first
significant detection of spectral parameter variation in an AXP. The
implications of these results are briefly discussed.
