s$^{-1}$ cm$^{-2}$. This is obviously a very crude estimate.

[ An EUVE spectrum was obtained for this source, the first time ever for a SXT. The source flux at these wavelengths is heavily dependent on the extinction, but the upper limit on $F_{\rm EUV}$ derived above appears consistent with both a simple extrapolation of the optical–UV flux observed and the EUVE flux inferred if a value of $N_{\rm H} \approx 10^{20}$ cm$^{-2}$ is assumed when dereddening the EUVE spectrum (Mauche et al. 2000; Hynes et al. 2000). ]{}

Peak-to-peak velocities
-----------------------

The mean peak-to-peak separation for all the observations is 18Å(1240 km s$^{-1}$) for H$\gamma$, 23Å (1470 km s$^{-1}$) for He[ii]{}, 21Å (1300 km s$^{-1}$) for H$\beta$ and 28Å (1280 km s$^{-1}$) for H$\alpha$. The S-wave is much less prominent in the Balmer lines [ and]{} we assume this represents the projected Keplerian velocity of the outer disk. [ The peak-to-peak separations have been found in well-known systems to overestimate the outer disk radius by about 20% because of sub-Keplerian motion or local broadening (Marsh 1998). This uncertainty is acceptable considering other assumptions made below.]{} For a Keplerian disk with an emissivity $\propto R^{-n}$, $\Delta v$ can be related to 