A NEW FREQUENCY-ANALYSIS OF PHOTOMETRIC-OBSERVATIONS OF THE BETA-CEPHEI STAR IL-VELORUM

We present a new frequency-analysis of Johnson UBV-data of the beta Ce phei star IL Vel, obtained between 1977 and 1979. This new analysis wa s inspired by more recent measurements of IL Vel in the Walraven five- colour photometric system. These data suggested the presence of freque ncies not found in the original analysis of the UBV-data. Rom the new analysis, we conclude that four frequencies can be identified with cer tainty in the variations of IL Vel: f0 = 5.464973 +/- 0.000005, f1 = 5 .363229 +/- 0.000006, f2 = 5.48838 +/- 0.00002 and f3 = 5.44184 +/- 0. 00003, in cycles per day. The frequencies f0, f2 and f3 form a closely spaced triplet.