A Comprehensive Spectral Analysis of the X-Ray Pulsar 4U 1907+09 from Two Observations with the Suzaku X-ray Observatory

Abstract

We present results from two observations of the wind-accreting X-ray pulsar 4U 1907+09 using the Suzaku Observatory. The broadband time-averaged spectrum allows us to examine the continuum emission of the source and the cyclotron resonance scattering feature at ~19 keV. Additionally, using the narrow CCD response of Suzaku near 6 keV allows us to study in detail the Fe K bandpass and to quantify the Fe Kβ line for this source for the first time. The source is absorbed by fully covering material along the line of sight with a column density of N _H ~ 2 × 10²² cm^-2, consistent with a wind-accreting geometry, and a high Fe abundance (~3-4 times solar). Time- and phase-resolved analyses allow us to study variations in the source spectrum. In particular, dips found in the 2006 observation which are consistent with earlier observations occur in the hard X-ray bandpass, implying a variation of the whole continuum rather than occultation by intervening material, while a dip near the end of the 2007 observation occurs mainly in the lower energies implying an increase in N_{{H}} along the line of sight, perhaps indicating clumpiness in the stellar wind.