We present time-resolved spectroscopy and photometry of SDSS J100658.40 + 233724.4 , which we have discovered to be an eclipsing cataclysmic variable with an orbital period of 0.18591324 days ( 267.71507 min ) .
The observed velocity amplitude of the secondary star is 276 \pm 7 km s ^ { -1 } , which an irradiation correction reduces to 258 \pm 12 km s ^ { -1 } .
Doppler tomography of emission lines from the infrared calcium triplet supports this measurement .
We have modelled the light curve using the lcurve code and Markov Chain Monte Carlo simulations , finding a mass ratio of 0.51 \pm 0.08 .
From the velocity amplitude and the light curve analysis we find the mass of the white dwarf to be 0.78 \pm 0.12 { M } _ { \odot } and the masses and radii of the secondary star to be 0.40 \pm 0.10 { M } _ { \odot } and 0.466 \pm 0.036 { R } _ { \odot } , respectively .
The secondary component is less dense than a normal main sequence star but its properties are in good agreement with the expected values for a CV of this orbital period .
By modelling the spectral energy distribution of the system we find a distance of 676 \pm 40 pc and estimate a white dwarf effective temperature of 16500 \pm 2000 K .