CCD photometry of the newly discovered intermediate polar RE 0751+14.

CCD photometry in the standard R_c band of the BVRI_c system is presented of the EUV source RE0751+14, which was discovered from ROSAT WFC observations to be an intermediate polar type of cataclysmic variable. Observations were secured on a total of five nights, with the longest continuous run being 7.7 h. The data on all nights confirm the 13.9-min periodicity seen in the X-ray data, but the amplitude of this variation is strongly modulated from the mean of about 10 per cent up to values of about 20 per cent and down to zero. On the three longer runs, evidence is found for an additional period of 1.14 h, which might serve to explain the modulated behaviour of the 13.9-min variation. There are additional longer-term variations (of the order of hours) ranging over 0.3 mag seen on individual nights, and the total range of differential R_c-band magnitudes for RE0751+14 reported here is 0.5 mag. When these data are phased according to the tentatively proposed orbital period of the system of 5.5±0.5 h, the resultant light curve is a scatter diagram. This set of data is not sufficient to establish a periodicity for the longer-term variations.