COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3322 Konkoly Observatory Budapest 24 April 1989 HU ISSN 0374-0676 1987 BV PHOTOELECTRIC OBSERVATIONS OF CG Cyg This eclipsing binary was observed from 7 July through 22 July 1987 with the 1.2 m Kryonerion telescope and a single channel photon counting photometer described by Dapergolas and Korakitis (1987). The photometer employs a high gain 9789 QB phototube and conventional BV filters. Its output is fed directly to a microcomputer enabling rapid data access. Castle et al. (1977), Milone et al. (1979), Jassur (1980), Naftilan and Milone (1985), Sowell et al. (1987), and finally Dapergolas et al. (1988) have also presented photometric observations for this star. The data reduction method is the standard one. The check and comparison stars are the stars a and b, respectively named by Yu (1923). The data were obtained with an accuracy of +-0.015 mag. Table I lists the dates of observations and phases covered whereas Figures 1 and 2 summarize the results for B and V colours. Table I Date Phase 7 July 1987 .24-.44 8 July 1987 .68-.03 9 July 1987 .31-.44 10 July 1987 .88-.21 16 July 1987 .45-.72 22 July 1987 .88-.08 In Table II the times of minima and the O-C values are listed for the V and B bands respectively. Times of minima are calculated using the method described by Kwee and van Woerden (1956) whereas the O-C values were determined from the linear ephemeris T=2439425.1221d+0.631141d*E given by Milone and Ziebarth (1974). From the V light curve presented here, it can be suggested that there are irregularities outside the eclipses already reported by Milone et al. (1979). The observed difference between the primary and secondary minima is 0.30 mag and 0.41 mag for the V and B colours respectively, whereas these values are reported as being 0.30 mag and 0.34 mag by Dapergolas et al. (1988) indicating that the variation in the depth is similar for both colours. The observed variation of the differences between the primary and secondary minima is probably due to a variably asymmetric light curve already reported by Milone et al. (1979). [FIGURE 1] [FIGURE 2] Table II Type of Heliocentric (O-C) Heliocentric (O-C) minima Jul. Day phase Jul. Day phase Primary 2446987.4749 0.0339 2446987.4746 0.0339 +-0.0003 +-0.0003 Secondary 2446993.4694 0.5317 2446993.4687 0.5305 +-0.0003 +-0.0003 Primary 2446999.4658 0.0326 2445990.4655 0.0322 +-0.0002 +-0.0004 A. DAPERGOLAS and E. KONTIZAS M. KONTIZAS National Observatory of Athens University of Athens Astronomical Institute Laboratory of Astrophysics P.O. Box 20048 Panepistimiopolis GR-118-10 Athens GR-151-71 Athens Greece Greece References: Castle, K.G., Milone, E.F., Robb, R.M., and Swadrom, D. 1977, Bull. A.A.S., 9, 623. [BIBCODE 1977BAAS....9..623C ] Dapergolas, A., Kontizas, E., and Kontizas, M. 1988, Inf. Bull. Var. Stars, No. 3249. Dapergolas, A., and Korakitis, R. 1987, Publ. Not. Obs. Athens, Ser. II, No. 28. Jassur D.M.Z. 1980, Astrophys. Space Sci., 67, 19. [BIBCODE 1980Ap&SS..67...19J ] Kwee, K.K., and van Woerden, H. 1956, Bull. Astr. Inst. Netherlands, 12, 327. [BIBCODE 1956BAN....12..327K ] Milone, E.F., and Ziebarth, K.E. 1974, Publ. Astron. Soc. Pacific, 86, 684. [BIBCODE 1974PASP...86..684M ] Milone. E.F., Castle, K.G., Swadrom, D., Burke, E.W. Hall, D.S., Michlovic, J.E. and Zissell, R.E. 1979 Astron. J., 84, 417. [BIBCODE 1979AJ.....84..417M ] Naftilan, S.A., and Milone, E.F. 1985, Astron. J. 90, 761. [BIBCODE 1985AJ.....90..761N ] Sowell, R.J., Wilson, W.J., Hall, D.S., and Peyman, C.P. 1987, Publ. Astron. Soc. Pacific, 98, 407. [BIBCODE 1987PASP...99..407S ] Yu, C.S. 1923, Astrophys. J., 58, 75. [BIBCODE 1923ApJ....58...75Y ]