1020009

The mass transfer and accretion mechanisms in SFXTs are key questions to be answered in order to place the SFXTs in the wider context of HMXB systems. Current theories centre on mass transfer via isotropic but inhomogeneous (clumpy) winds but some systems also show evidence of disk-like structures around the supergiant analogous to those seen in Be/X-ray binaries. We propose a campaign of periastron observations of 2 SFXTs with known ephemerides following on from the accepted AO-9 programme Probing the nature of the circumstellar environment around periastron in SFXTs (P.I. Drave PropID 0920016). Using both INTEGRAL and XMM-Newton we will measure the instantaneous accretion rate emission spectrum and time variability generated on and around the neutron star. Now that the orbital parameters of these SFXTs are well-determined targeted continuous broad-band observations around periastron provide us with the best opportunity to use the (assumed) neutron star as a direct probe of the circumstellar wind environment. To achieve the goals outlined in this proposal we request 467ks of fixed time INTEGRAL observations complemented with 80ks of simultaneous XMM-Newton observations. [truncated! Please see actual data for full text]