A Spectral Analysis of the X-Ray Pulsar 4U 1907+09 obtained at thePeriastron Passage with the XMM-Newton Observatory

We present results from a 20 ksec observation of the wind-accreting X-ray pulsar 4U 1907+09 obtained using the XMM-Newton Observatory at the periastron passage. The XMM-Newton spectrum allows us to study the continuum emission and the emission line at 6.4 keV with the high sensitivity and appreciable energy resolution of the EPIC CCDs. We investigate the total source spectrum at the periastron passage and the spin phase resolved spectroscopy of the source during this time interval. We find a soft excess in both the total spectrum and the spin phase resolved spectroscopy. The excess is succesfully modeled by a blackbody emission-model of kT in a range 0.07-0.15 keV which varies with the spin phase. We detect a delay in the spin pulse of about 0.1 phase between energies 0.3-1.0 keV and 3-10 keV indicative of reprocessing in the system. We also studied the neutral and ionized absorption on the spin phase of the pulsar. We present the total spectrum and the spin phase-resolved spectra using a warm absorber model in relation to the absorption and reprocessing detected with spectral and timing analysis of the source. We sucessfully fit a warm-absorber model together with a power-law emission-model without the need for a blackbody emission-model which indicates that the soft excess may be a result of incorrect attribution of absorption for this source. We find that the logarithm of the ionization parameter varies between 1.4 and 2.6 (over the spin phase) indicating that the absorber to be on the magnetosphere or the inner part of an accretion disk existing during the periastron passage. The aborption can also be modeled by variable neutral abundances of material in the line of sight with ratio to solar value of Fe 2.7-4.2, Si 2.6-3.3, Al 7.8-13.7, and Ne 1-1.65. However, a blackbody model is necessary at all times.