Probing the Superorbital Modulation in the Supergiant X-ray binary 4U 1909+07

We propose XMMNewton observations of the Comptonthick windfed SupergiantXray binary (SGXB) 4U 1909+07 (hereafter 4U1909) for 20(35) ks during themaximum (minimum) of its 15.2 day superorbital cycle. With the first XMMobservation of the source we will test the physical mechanisms driving its 15.2day modulation, in particular whether it is caused by Corotation InteractionRegions (hereafter, CIRs). By constraining the Fe fluorescence complex atdifferent superorbital phases we will probe largescale (high density andvelocity) structures threading the wind of the B03 I donor star. Additionally,the large effective area and excellent timing resolution of EPIC will allow usto probe superorbital changes in the size and geometry of the circumstellar material by measuring changes in pul truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]