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We report results from an observation with the XMM-Newton observatory of aunique X-ray pulsar 4U 1626-67. EPIC-pn data during the current spin-up phaseof 4U 1626-67 have been used to study pulse phase dependence of low energyemission lines. We found strong variability of low energy emission line at0.915 keV with the pulse phase, varying by a factor of 2, much stronger thanthe continuum variability. Another interesting observation is that behavior ofone of the low energy emission lines across the pulse phase is quite differentfrom that observed during the spin-down phase. This indicates that thestructures in the accretion disk that produce pulse phase dependence ofemission features have changed from spin-down to spin-up phase. This is wellsupported by the differences in the timing characteristics (like pulseprofiles, QPOs etc) between spin-down and spin-up phases. We have also foundthat during the current spin-up phase of 4U 1626-67, the X-ray pulse profilebelow 2 keV is different compared to the spin-down phase. The X-ray light curvealso shows flares which produce a feature around 3 mHz in power densityspectrum of 4U 1626-67. Since flares are dominant at lower energies, thefeature around 3 mHz is prominent at low energies.

Changes in the pulse phase dependence of X-ray emission lines in 4U 1626-67 with a torque reversal