ON THE PULSATIONAL STABILITY OF THE PRE-WHITE DWARF STAR PG 1707+427

The pulsating pre-white dwarf star PG 1707 + 427 has been observed with time-series photometry for more than 291 hr spanning four observing seasons (1987-1990). The principal pulsational band of periods near 448 s, found in earlier data, was observed to vary regularly in amplitude, suggesting that it was unresolved. By dividing the data into separate blocks of time, we were able to resolve this peak into two components (A and B) with periods near 447.16 and 448.95 s. Both modes appeared to be relatively constant in amplitude to the accuracy of our measurements over the observed span of time. Although we found it possible to fit our data to an emphemeris for both periods A and B, we suspect that these are not truly stable modes. The 1.3 day beat period between period A and period B is fairly consistent, suggesting that it may be related to the rotation of the star.