COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1178 Konkoly Observatory Budapest 1976 September 13 PHOTOMETRIC OBSERVATIONS OF LX PERSEI LX Persei (BD+47d781, BV 307, R.A. (1900) 03h06.4m, Dec. (1900) +47d43.5', V = 8.20) was reported to be an eclipsing variable by Strohmeier et al. (1962). The depth of the primary eclipse was about 1.1m (photographic), but no secondary eclipse was detected. FitzGerald (1964, 1974) and Weiler (1974) have studied the system spectroscopically, and have found it to consist of two G-type stars (G5IV + G5IV?) of nearly equal mass. One component has strong CaII emission; for this and other reasons, LX Per is a strong candidate for inclusion in the "RS CVn" class of eclipsing binary stars (Hall, 1972). FitzGerald (1964) noted that the spectroscopic properties of LX Per were inconsistent with the lack of a secondary eclipse. For this reason, photometric observations of this star were made, primarily to search for such an eclipse. OBSERVATIONS: Observations were made in 1967 using the 48 cm reflector at the David Dunlap Observatory, and in 1970 using the no. 3 41 cm reflector at Kitt Peak National Observatory. The comparison star was HD 20192 (m = 7.8, spectral type G9II). Magnitudes were corrected for differential extinction and were reduced to differential values on the UBV system. This was accomplished by use of appropriate filters and by reference to secondary UBV standards in the alpha Persei cluster. Phases were calculated using the epoch JD 2427033.120 given in the General Catalogue of Variable Stars and the best spectroscopic period 8.038207 (+- 0.000117) days, covering the period 1962 to 1973 (FitzGerald 1974). The results are presented in the table and shown on the figure. DISCUSSION: The shoulder of the secondary eclipse was observed successfully on two dates. The eclipse has a depth of at least 0.165 in both B and V light. The similar behaviour in both B and V light is consistent with the near-identical properties of the two components of the system. The phase of secondary eclipse is not the same on the two dates JD 2439825 and JD 2440886. This may be due to period changes between 1962 and 1973, or due to a real variation in the phase of secondary eclipse in a system of constant period. Fitting the two secondary eclipses together produces a period of 8.038500 day, which is not consistent with the spectroscopic period of 8.038207 (+- 0.000117) days. On the other hand, several other "RS CVn" stars show variations in the phase of secondary eclipse. Further photometric observations of this system would be desirable, but the near-integral period makes the system difficult to observe. ACKNOWLEDGEMENTS: This work was supported by a grant from the National Research Council of Canada. JOHN R. PERCY Department of Astronomy, University of Toronto Toronto, Canada, M5S 1A7 REFERENCES FitzGerald, M.P. 1964. Publ. David Dunlap Observatory 2, 417. [BIBCODE 1964PDDO....2..417F ] FitzGerald, M.P. 1974. J. Roy. Ast. Soc. Canada 68, 23. [BIBCODE 1974JRASC..68...23F ] Hall, D.S. 1972. Publ. Ast. Soc. Pacific 84, 323. [BIBCODE 1972PASP...84..323H ] Strohmeier, W., Knigge, R. and Ott, H. 1962. Veroff. Remeis Sternwarte Bamberg 5, 3. TABLE JD Cycle and Phase DeltaV DeltaB 2439786.6889 1586.6186 0.304 800.5729 1588.3459 0.297 .6778 .3589 0.286 825.5097 1591.4482 0.320 .6451 .4650 0.309 .6722 .4684 0.321 .7139 .4736 0.362 .7563 .4788 0.429 829.6000 .9570 0.297 844.6167 1593.8252 0.305 851.5542 1594.6882 0.305 2440886.7271 1723.4698 0.299 .7363 .4710 0.310 .7542 .4732 0.324 .7653 .4746 0.341 -0.014 .7799 .4764 0.358 -0.006 .7868 .4772 0.360 +0.013 .8042 .4794 0.387 +0.027 .8160 .4809 0.402 +0.015 .8285 .4824 0.408 +0.051 .8333 .4830 0.421 +0.059 .8451 .4845 0.458 +0.068 .8563 .4859 0.453 +0.088 .8694 .4875 0.465 +0.104 [FIGURE 1]