We report the results of observations of V4633 Sgr ( Nova Sagittarii 1998 ) during 1998-2000 .
Two photometric periodicities were present in the light curve during the three years of observations : a stable one at P = 3.014 h , which is probably the orbital period of the underlying binary system , and a second one of lower coherence , approximately 2.5 per cent longer than the former .
The latter periodicity may be a permanent superhump , or alternatively , the spin period of the white dwarf in a nearly synchronous magnetic system .
A third period , at P = 5.06 d , corresponding to the beat between the two periods was probably present in 1999 .
Our results suggest that a process of mass transfer took place in the binary system since no later than two and a half months after the nova eruption .
We derive an interstellar reddening of E ( B - V ) \sim 0.21 from our spectroscopic measurements and published photometric data , and estimate a distance of d \sim 9 kpc to this nova .