A photometric analysis of BW Vulpeculae

New times of maximum light have been determined and combined with all the previous times available in the literature to anlyse the period variation of BW Vul. It is found that the period increase can be well represented by a smooth variation of the form Tmax = 2439828.5534 + 0.20103747 x E + 8.79 x 10-11 x E2 which implies a period increase rate of 2.5 s/century. The O-C residuals suggest a sinusoidal behaviour relative to the above ephemeris. To study a possible cause of these variations, the radial velocities available over the last sixty years were analysed. Significant systemic velocity variations were found; it is suggested that such variations may be produced by photospheric oscillations about a dynamic equilibrium point, as a consequence of the existence of more than one overtone acting simultaneously. 32 refs., 4 figs., 7 tabs. (author)