Kinematical studies of the low-mass X-ray binary GR Mus (XB 1254-690)

We present simultaneous high-resolution optical spectroscopy and X-ray data of the X-ray binary system GR Mus (XB 1254-690), obtained over a full range of orbital phases. The X-ray observations are used to re-establish the orbital ephemeris for this source. The optical data include the first spectroscopic detection of the donor star in this system through the use of the Doppler Tomography technique on the Bowen fluorescence blend (similar to 4630-4650 angstrom). In combination with an estimate for the orbital parameters of the compact object using the wings of the He it lambda 4686 emission line, dynamical mass constraints of 1.20 <= M-X/M-circle dot <= 2.64 for the neutron star and 0.45 <= M-2/M-circle dot <= 0.85 for the companion are derived