Searching for disk outflows in BH X-ray binaries: measuring BH masses

We propose to use XMM-Newton to obtain a target of opportunity observation of a transient black hole X-ray binary in the high-soft state for 50 ks. If we discover absorption lines in the X-ray spectra we can track the motion of the black hole around the binary's center of mass via the Doppler shifts of the lines associated with the accretion disc wind. Using this observation we can determine black hole masses and test assumptions that have been made in current BH mass estimates.