We report follow-up observations of a new white dwarf/red dwarf binary HS 2237+8154 , identified as a blue variable star from the Hamburg Quasar Survey .
Ellipsoidal modulation observed in the R 
band as well as the { \mathrm { H } \alpha } radial velocity variations measured from time-resolved spectroscopy determine the orbital period to be \mbox { $P _ { orb } $ } = 178.10 \pm 0.08 min .
The optical spectrum of HS 2237+8154 is well described by a combination of a \mbox { $T _ { \mathrm { eff } } $ } = 11 500 \pm 1500 K white dwarf ( assuming \log g = 8 ) and a dM3.5 \pm 0.5 secondary star .
The distance implied from the flux scaling factors of both stellar components is d = 105 \pm 25 pc .
Combining the constraints obtained from the radial velocity of the secondary and from the ellipsoidal modulation , we derive a binary inclination of i \simeq 50 ^ { \circ } -70 ^ { \circ } and stellar masses of \mbox { $M _ { \mathrm { wd } } $ } = 0.47 - 0.67 M _ { \odot } and \mbox { $M _ { \mathrm { sec } } $ } = 0.2 - 0.4 M _ { \odot } .
All observations imply that the secondary star must be nearly Roche-lobe filling .
Consequently , HS 2237+8154 may be either a pre-cataclysmic variable close to the start of mass transfer , or – considering its orbital period – a cataclysmic variable that terminated mass transfer and entered the period gap , or a hibernating nova .