The detection of four new pulsation periods in PG 1159-035.

The paper reports the detection of four new period bands, at 560 s, 524 s, 508 s and 414 s, in the optical light curve of PG 1159-035 from the analysis of recent observations (Feb. 1987). Three of the four frequencies correspond to previously unidentified peaks in the 1985 Exosat data. In contrast to the clearly unstable nature of the new bands, the eight previously identified optical period bands have remained stable in period and amplitude within the errors of the analysis. The unexpected appearance of the new periods will provide a stringent test of the seismological models of Kawaler (1987) which are based on period spacing. The way in which these new frequencies appeared provides new insight into possible filter mechanisms responsible for mode selection in these stars.