THE DISCOVERY OF VARIABLE POLARIZATION OVER THE 13.9 MINUTE SPIN PERIOD OF THE INTERMEDIATE POLAR RE-0751+14

The total (peak-to-peak) circular polarization variation over the 13.9 minute spin period of RE 0751 + 14 on 1992 October 26 was 4.2% +/- 0.6% in the I band (830 nm) and 2.2% +/- 0.3% in the R band (690 nm), with slightly stronger negative extremes and a faster transition from the negative to the positive values. The linear polarization reached about 2% in I and 0.8% in R. Our analysis suggests cyclotron emission from two extended regions near the opposite magnetic poles of the white dwarf, and a field strength B > 5 MG (1 MG = 10(6) G). Fitting the existing cyclotron models to the relative amplitudes of the polarization and intensity variations in R and I bands required field strengths in the range 8-18 MG, with the dimensionless plasma parameter of the emission region A = 10(8)-10(5). Larger A values are needed at lower field strengths. The position angle variability could be tentatively explained with the inclination of the magnetic white dwarf spin axis i = 45-degrees-70-degrees and the two cyclotron emission regions 35-degrees-60-degrees off from the rotational poles. The power spectra of the I- and R-band intensity modulation are dominated by the cyclotron-originated spin period peak at 13.9 minutes, but secondary maxima are seen at approximately 15 minutes. The UBV bands show maximum modulation at the period of 14.5 minutes, which could be the beat period in the system having a binary period of about 5 hr.