We present extensive spectroscopy and photometry of the dwarf nova V630 Cassiopeiae .
A late-type ( K4-5 ) absorption spectrum is easily detectable , from which we derive the orbital parameters .
We find a spectroscopic period of P = 2.56387 \pm 4 \times 10 ^ { -5 } days and a semiamplitude of K _ { 2 } = 132.9 \pm 4.0 km s ^ { -1 } .
The resulting mass function , which is a firm lower limit on the mass of the white dwarf , is then f ( M ) = 0.624 \pm 0.056 M _ { \odot } .
The secondary star is a “ stripped giant ” , and using relations between the core mass and the luminosity and the core mass and the radius we derive a lower limit of M _ { 2 } \geq 0.165 M _ { \odot } for the secondary star .
The rotational velocity of the secondary star is not resolved in our spectra and we place a limit of V _ { rot } \sin i < 40 km s ^ { -1 } .
The long-term light curve shows variations of up to 0.4 mag on short ( 1-5 days ) time scales , and variations of 0.2-0.4 mag on longer ( 3-9 months ) time scales .
In spite of these variations , the ellipsoidal light curve of the secondary star is easily seen when the data are folded on the spectroscopic ephemeris .
Ellipsoidal models fit to the mean light curve give an inclination in the range 66.96 \leq i \leq 78.08 degrees ( 90 per cent confidence ) .
This inclination range , and the requirement that M _ { 2 } \geq 0.165 M _ { \odot } and V _ { rot } \sin i < 40 km s ^ { -1 } yields a white dwarf mass of M _ { 1 } = 0.977 ^ { +0.168 } _ { -0.098 } M _ { \odot } and a secondary star mass of M _ { 2 } = 0.172 ^ { +0.029 } _ { -0.012 } M _ { \odot } ( 90 per cent confidence limits ) .
Our findings confirm the suggestion of Warner ( 1994 ) , namely that V630 Cas is rare example of a dwarf nova with a long orbital period .