UBV PHOTOMETRY OF THE BETA-CEPHEI TYPE VARIABLE-STARS .5. 16(EN) LACERTAE

Extensive B, BV and UBV photoelectric observations of this eclipsing s ystem with a beta Cephei primary are presented and analyzed. It is fou nd that the primary's light variation consists of nine sinusoidal term s. The three largest amplitude terms with periods P1 = 0.d16917, P2 = 0.d17079 and P3 = 0.d18171 have been known before, while the six faint er ones were discovered in the present analysis. The amplitudes of the latter range from 2.1 +/- 0.14 to 0.5 0.15 mmag. The strongest has a period equal to half the orbital period, but cannot be accounted for b y an ''ellipticity effect''. The next one in the order of decreasing a mplitude has a period equal to 0.d139; it may be an overtone of any of the three strongest terms. The fifth term is the lowest order harmoni c of the first, and the last three are the first-order combination ter ms with frequencies 1/P2 + 1/P3, 1/P1 + 1/P3 and 1/P1 + 1/P2. For the three strongest terms, the color amplitude to visual amplitude ratios, A(U-V)/A(V), and the color phase minus visual phase differences, PHI( U-V) - PHI(V), are derived and used to determine the spherical harmoni c orders of the underlying oscillations. The strongest term is identif ied with a radial mode, while the fainter two with l = 2 and l = 1 mod es. Thus, the close P1, P2 doublet is not due to rotational splitting of two m states belonging to the same l, but consists of two modes of different l. The night-to-night character of the light variability of 14 Lac, one of the comparison stars in this investigation, is confirme d.