is shown in Fig. \[fig:sumlines\], after the underlying continuum was normalized to unity. When available, multiple spectra were summed up to increase the S/N of the spectra. A comparison between the most comprehensive datasets (Apr. 17 and Jul. 4), where measurement errors can be minimized, shows that the two strongest lines, H$\alpha$ and He[ii]{}, did not change significantly. We conclude that there do not seem to be any long term variations. The average properties of the lines are summed up in Table. \[tab:lines\] (the quoted errors are the rms of the measurements).

In all our spectra the blue side of the absorption troughs in H$\gamma$ and H$\beta$ is less [ strong]{} than the red side. The measured central wavelengths of the absorptions are redshifted compared to the rest wavelength (which could be an artefact of the method we used to remove the double peaked emission). Fitting a gaussian to the red part of the absorption while ignoring (but not subtracting) the emission lines gave higher equivalent widths (2.4Åfor H$\gamma$ and 2.0Å for H$\beta$) and better agreement with the rest wavelength (7Å redshift for both instead of 15Å). Similar absorption redshifts were reported by Callanan et al. (1995) for GRO J0422+32. 