High time resolution spectroscopic observations of the ultra-compact helium dwarf nova ‘ SN 2003aw ’ in its quiescent state at V \sim 20.5 reveal its orbital period at 2027.8 \pm 0.5 seconds or 33.80 minutes .
Together with the photometric “ superhump ” period of 2041.5 \pm 0.5 seconds , this implies a mass ratio q \approx 0.036 .
We compare both the average and time-resolved spectra of ‘ SN 2003aw ’ and SDSS J124058.03 - 015919.2 ( 10 ) .
Both show a DB white dwarf spectrum plus an optically thin , helium-dominated accretion disc .
‘ SN 2003aw ’ distinguishes itself from the SDSS source by its strong calcium H & K emission lines , suggesting higher abundances of heavy metals than the SDSS source .
The silicon and iron emission lines observed in the SDSS source are about twice as strong in ‘ SN 2003aw ’ .
The peculiar “ double bright spot ” accretion disc feature seen in the SDSS source is also present in time-resolved spectra of ‘ SN 2003aw ’ , albeit much weaker .