COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 1297 Konkoly Observatory Budapest 1977 July 4 FURTHER LIGHT CURVE VARIATIONS OF SZ PISCIUM The eclipsing variable SZ Psc (HD 219113), which is a member of the RS CVn class (Hall 1976), recently has been studied by Jakate et al. (1976). In that study photometry from two epochs was presented which indicated that the light curve is highly variable. Data obtained by Bakos in 1957 exhibited a pronounced sinusoidal wave (0.2 mag amplitude, maximum near phase 0.7) while data obtained in 1974 showed this feature to be absent. A few observations made in intermediate years indicated that the wave was present at close to the 1957 amplitude but that it was not migrating in phase. Since continuing observation will be useful in studying the variation of the wave, the brightness of SZ Psc was measured at times of opportunity on nine nights during December 1976 using the 42-inch (107 cm) telescope at Lowell Observatory. The accompanying Table gives the observations which consist of magnitude differences, SZ Psc minus HD 219018, corresponding to passbands chosen to approximate the V and I bands of the UBVRI system. The photometric system used was similar to that described by Fernie (1974), differing only in the substitution of an ITT F4085 photomultiplier. It will be noted that the comparison star is that used by Jakate et al.; the time of mid- eclipse, however, occurred about an hour later than predicted by the non-linear elements of that study. Therefore, the phases listed have been computed using the formula JDhel= 2442308.7671 + 3.965552E which Jakate et al. determined from the times of their photoelectric primary minima. Table JDhel Phase Delta Delta JDhel Phase Delta Delta 2443000+ nu (nu-i) 2443000+ nu (nu-i) 117.6683 0.9820 -0.258 0.369 117.7169 0.9942 -0.170 0.403 117.6750 0.9837 -0.245 0.375 117.7203 0.9951 -0.171 0.399 117.6757 0.9839 -0.243 0.373 117.7212 0.9953 -0.178 0.396 117.6766 0.9841 -0.243 0.366 118.5563 0.2059 -0.446 0.317 117.6798 0.9849 -0.237 0.378 118.5595 0.2067 -0.452 0.309 117.6807 0.9851 -0.234 0.380 119.5626 0.4597 -0.333 0.324 117.6816 0.9853 -0.232 0.378 119.5655 0.4604 -0.331 0.329 117.6845 0.9861 -0.227 0.378 119.7394 0.5043 -0.318 0.331 117.6866 0.9866 -0.222 0.382 119.7431 0.5052 -0.307 0.345 117.6876 0.9869 -0.219 0.384 121.5875 0.9703 -0.344 0.304 117.6913 0.9878 -0.211 0.385 121.5996 0.9732 -0.343 0.346 117.6923 0.9880 -0.213 0.387 122.5474 0.2124 -0.445 0.322 117.6932 0.9883 -0.214 0.382 122.5503 0.2131 -0.451 0.317 117.6965 0.9891 -0.207 0.385 122.5535 0.2139 -0.447 0.319 117.6875 0.9894 -0.208 0.385 123.7341 0.5116 -0.329 0.316 117.6985 0.9896 -0.202 0.385 124.5489 0.7171 -0.522 0.297 117.7017 0.9904 -0.201 0.387 124.5524 0.7180 -0.525 0.302 117.7025 0.9906 -0.194 0.394 126.6121 0.2374 -0.430 0.296 117.7056 0.9914 -0.192 0.392 128.5659 0.7301 -0.534 0.299 117.7065 0.9916 -0.190 0.397 128.5694 0.7309 -0.533 0.294 117.7074 0.9919 -0.190 0.399 128.5773 0.7329 -0.526 0.299 117.7106 0.9927 -0.184 0.397 128.5803 0.7337 -0.525 0.308 117.7116 0.9929 -0.184 0.393 128.5834 0.7345 -0.527 0.312 117.7126 0.9932 -0.177 0.402 117.7158 0.9940 -0.180 0.397 [FIGURE 1] The accompanying figure illustrates the 1976.9 light variation. Although the period is almost exactly four days, the phasing was such that it was possible to obtain observations at the quadratures and during both eclipses. The wave clearly has been reestablished with an amplitude of at least 0.075 mag. Further, the depth of secondary eclipse seems to have increased significantly while the level of mid-primary eclipse is higher that at former epochs. This suggests that the wave maximum has shifted toward increasing phase. The present (v-i) color curve provides the first measurement of the color of the wave in this system. The wave is slightly bluer than the system as a whole. Since the secondary contributes significantly more light at longer wavelengths, the contrast between bright and dark hemispheres is lower in the infrared than in the visual. Finally, one notes that on the average the system has become brighter and bluer since 1974. I wish to thank the staff of Lowell Observatory, especially Robert Millis, for the most pleasant and productive observing session which lead to these results. JOEL A. EATON Goddard Space Flight Center Greenbelt, Maryland 20771 U.S.A. References: Fernie, J.D. 1974, Pub. Astr. Soc. Pacific, 86, 837 [BIBCODE 1974PASP...86..837F ] Hall, D.S. 1976, "The RS CVn Binaries and Binaries with Similar Properties", Proceedings of the I.A.U. Colloquium No. 29, Vol. I. 287 [BIBCODE 1976ASSL...60..287H ] Jakate, S., Bakos, G.A., Fernie, J.D., and Heard, J.F. 1976, Astr. J., 81, 250 [BIBCODE 1976AJ.....81..250J ]