COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1657 Konkoly Observatory Budapest 1979 August 8 FURTHER OBSERVATIONS OF ET ANDROMEDAE A solution for the spectroscopic orbit of the binary Ap variable ET And = HD 219749 has recently been published by Ouhrabka and Grygar (1979; hereafter OG). Here we report independent spectroscopic observations which support their solution. Also, we briefly describe the variations in spectral line strengths which occur in this star and which, we suggest, will be found ultimately to correlate with the photometric variations. Twenty-six radial velocities measured by this writer and not previously published are available. Four of these are from 1.2 nm/mm grating plates obtained at the David Dunlap Observatory (DDO); three are from Dominion Astrophysical Observatory (DAO) archival prism plates of dispersion 5.1 and 3.0 nm/mm; the remainder are from 1.5 nm/mm DAO grating plates. All plates were measured on oscilloscopic-setting comparators. The data are presented in Table 1, where the phase is relative to the time of periastron passage, and the (O-C)s are relative to the velocity curve as determined by OG. These radial velocities are plotted in Figure 1, where the DDO velocities are represented by crosses, the higher dispersion DAO velocities by large open circles, and the other DAO velocities by small circles. The solid curve is the velocity curve from OG. The broken line results from a least-squares correction procedure applied to these new velocities and using the OG elements as preliminary values. The differences between these two curves are not considered to be significant. In particular, the orbital period of 48.304 days is confirmed. Spectral line variations have long been known to occur in this system (cf. Renson 1977 and references therein). While visual examination of these plates does not permit a completely reliable estimation of the degree of variation of relatively strong lines such as the SiII lambda4128-30 pair, it is strikingly apparent that relatively weaker lines are variable in strength. To the eye, the most obvious variations occur in the lambda3954 line which can be attributed to SiII. In this respect HD 219749 is similar to HD 73340 (Hube and Walker 1976). This line varies from complete invisibility to approximately two-thirds the strength of the K-line. (Note that the K-line is of interstellar origin although there may be a weak, blending stellar component since the plate-to-plate velocity is not as constant as one would expect. The average heliocentric K-line velocity is -5.7 km/s.) An unidentified line near lambda3906, the Sr-Si complex near lambda4077, and groups of lines in the regions lambda4150-4230 and lambda4500-4630 are also clearly variable in strength. These lines do not seem to vary relative to one-another in a consistent manner. For example, when lambda3954 is near maximum strength lambda3906 is not visible; when lambda3954 is near half-maximum lambda3906 may, or may not, be visible. The line strengths do not vary in phase with the orbital velocity. In Figure 1 we have indicated with strokes the approximate line strengths at various phases in the orbit. In their present form the data on line strengths are not sufficient to permit an independent search for periodicities, nor to make a reliable comparison with the several photometric periods which have been proposed. However, it is interesting to note that the intervals between the three maxima of lambda3954 do correspond to integral multiples of the 1.618 day period suggested by Renson (1977). [FIGURE 1] Fig. 1. Radial velocity curve of ET And and spectral line strength variations. Table 1 ------------------------------------------------- J.D.(Hel) Dispersion RV O-C Phase 2400000+ (A/mm) (km/s) (km/s) ------------------------------------------------- 38613.976 51 -19.3 -5.8 0.292 38987.836 30 29.4 17.2 0.031 38990.886 30 -3.8 4.4 0.095 39680.959 15 -7.0 3.7 0.381 40449.955 15 -15.4 -2.1 0.301 40803.722 12 0.5 -0.6 0.624 40809.805 12 13.4 2.7 0.750 40835.855 15 -12.3 1.3 0.290 41147.850 12 15.2 4.6 0.749 41159.747 12 35.9 6.3 0.998 42644.977 15 11.7 1.7 0.742 42648.982 15 19.8 0.8 0.825 42955.890 15 -9.7 4.9 0.179 42992.957 15 33.5 -2.8 0.946 43054.819 15 -11.4 3.3 0.227 43081.726 15 17.6 3.4 0.784 43102.732 15 -10.3 4.5 0.219 43104.638 15 -12.3 2.0 0.258 43330.886 15 24.1 -11.8 0.942 43331.924 15 24.8 -11.6 0.964 43366.890 15 4.9 -0.6 0.688 43367.804 15 3.6 -3.3 0.706 43368.828 15 18.9 10.6 0.728 43823.687 15 -4.8 8.6 0.144 43825.666 15 -18.7 -3.7 0.185 44063.817 15 -17.5 -6.4 0.115 ------------------------------------------------ DOUGLAS P. HUBE Department of Physics University of Alberta Edmonton, Alberta, Canada References: Hube, D.P. and Walker, E.N., 1976. Astron. Astrophys. 50, 55. [BIBCODE 1976A&A....50...55H ] Ouhrabka, M. and Grygar, J., 1979. I.B.V.S. No. 1600. Renson, P., 1977. Astron. Astrophys. 54, 277. [BIBCODE 1977A&A....54..277R ]