SMITH R.C., MEHES O., VANDE PUTTE D. and HAWKINS N.A.
Abstract (from CDS):
Simultaneous spectroscopic and photometric observations of the Z Cam type dwarf nova SY Cancri were used to obtain absolute flux calibrations. A comparison of the photometric calibration with a wide-slit spectrophotometric calibration showed that either method is equally satisfactory. A radial velocity study of the secondary star, made using the far-red Nai doublet, yielded a semi-amplitude of K2= 127±23 km/s. Taking the published value of 86±9 km/s for K1gives a mass ratio of q=M2/M1= 0.68±0.14; this is very different from the value of 1.13±0.35 quoted in the literature. Using the new lower mass ratio, and constraining the mass of the white dwarf to be within reasonable limits, then leads to a mass for the secondary star that is substantially less than would be expected for its orbital period if it satisfied a main-sequence mass-radius relationship. We find a spectral type of M0 that is consistent with that expected for a main-sequence star of the low mass we have found. However, in order to fill its Roche lobe, the secondary must be significantly larger than a main-sequence star of that mass and spectral type. The secondary is definitely not a normal main-sequence star.
stars: dwarf novae - stars: individual: SY Cnc - novae, cataclysmic variables