Intermediate resolution ( 0.5-1 Å ) optical spectroscopy of the cataclysmic variable SY Cnc reveals the spectrum of the donor star .
Our data enable us to resolve the orbital motion of the donor and provide a new orbital solution , binary mass ratio and spectral classification .
We find that the donor star has spectral type G8 \pm 2 V and orbits the white dwarf with P = 0.3823753 \pm 0.0000003 day , K _ { 2 } = 88.0 \pm 2.9 km s ^ { -1 } and V \sin i = 75.5 \pm 6.5 km s ^ { -1 } .
Our values are significantly different from previous works and lead to q = M _ { 2 } / M _ { 1 } = 1.18 \pm 0.14 .
This is one of the highest mass ratios known in a CV and is very robust because it is based on resolving the rotational broadening over a large number of metallic absorption lines .
The donor could be a slightly evolved main-sequence or descendant from a massive star which underwent an episode of thermal-timescale mass transfer .