COMMISSIONS 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 4086 Konkoly Observatory Budapest 14 September 1994 HU ISSN 0374 - 0676 FURTHER PHOTOELECTRIC OBSERVATIONS OF VW Cep IN R AND I The present report announces a sequel of the report which appeared in a previous issue of this publication (Arai, 1991). We wish to report on several findings resulting from our observations of the variation of time of minima over several years. As before, the observations were made with the 28-cm (f=2,800mm) Schmidt Cassegrain telescope, equipped with a single channel R I photometer (SSP-3, Optec Inc.) and Schott standard filters. The observations were performed altogether during 31 nights between December 1989 and November 1993. The total number of observations obtained were 1514 points for each color (Table 1). Throughout the course of the present observations we assumed constancy of the brightness of BD+74d889. All the observations have been transformed to Johnson's standard system. The obtained light and color curves in R and I in 1993 are shown in Figure 1. Figure 2 shows the O-C diagram where the data of Glownia (1988), Lloyd et al. (1992), Navratil (1994), Vinko (1989, 1993) and Wunder (1992) are also plotted together. Figure 2 clearly indicates that the period abruptly changed in about 1990, being in agreement with the previous result by Lloyd et al. (1992). We obtained the new light elements: Min(Hel. JD) = 2448155.0724 + 0.27830526d x E Figure 3 depicts the variations of DeltaR, DeltaI at maxima and minima respectively. It is noticeable from Figure 3 that the maxima I and II have clearly changed between 1992 and 1993. Table 1. The data of present observations Season Nights Data points minima I minima II 1989 Dec.- 1990 Jan. 9 499 4 2 1990 Sep.- 1990 Nov. 6 271 5 2 1991 Nov.- 1991 Dec. 6 234 4 2 1992 Oct.- 1992 Nov. 6 340 4 5 1993 Oct.- 1993 Nov. 3 170 3 2 Table 2. New times of minima of VW Cep Filter: R I Hel. J.Day E O-C Hel. J.Day E O-C 244... 244... 7892.0693 -945 -0.0046 7892.0698 -945 -0.0041 7895.9649 -931 -0.0053 7895.9641 -931 -0.0061 7896.9416 -927.5 -0.0027 7896.9403 -927.5 -0.0040 7899.0270 -920 -0.0046 7899.0274 -920 -0.0042 7905.0135 -898.5 -0.0016 7905.0121 -898.5 -0.0030 7912.9418 -870 -0.0050 7912.9439 -870 -0.0029 8155.0724 0 0.0000 8155.0735 0 0.0011 8185.9649 111 0.0006 8185.9650 111 0.0007 8191.9483 132.5 0.0005 8191.9486 132.5 0.0008 8200.9943 165 0.0015 8200.9940 165 0.0012 8206.0017 183 -0.0006 8206.0019 183 -0.0004 8206.1428 183.5 0.0014 8206.1423 183.5 0.0009 8219.9146 233 -0.0029 8219.9170 233 -0.0005 8600.0835 1599 0.0010 8600.0834 1599 0.0010 8602.0300 1606 -0.0007 8602.0307 1606 0.0001 8603.0063 1609.5 0.0016 8603.0091 1609.5 0.0044 8603.9812 1613 0.0024 8603.9819 1613 0.0031 8606.9049 1623.5 0.0039 8606.9042 1623.5 0.0032 8607.0386 1624 -0.0016 8607.0392 1624 -0.0010 8920.9686 2752 0.0001 8920.9689 2752 0.0004 8921.1071 2752.5 -0.0005 8921.1050 2752.5 -0.0026 8923.0538 2759.5 -0.0020 8923.0532 2759.5 -0.0026 8927.9264 2777 0.0003 8927.9264 2777 0.0003 8928.0644 2777.5 -0.0009 8928.0646 2777.5 -0.0007 8929.0411 2781 0.0018 8929.0395 2781 0.0002 8929.1750 2781.5 -0.0035 8929.1758 2781.5 -0.0027 8949.9108 2856 -0.0014 8949.9104 2856 -0.0018 8950.0474 2856.5 -0.0040 8950.0483 2856.5 -0.0031 9284.1569 4057 0.0000 9284.1567 4057 -0.0002 9284.0163 4056.5 -0.0014 9284.0176 4056.5 -0.0001 9284.9912 4060 -0.0008 9284.9915 4060 -0.0003 9292.9246 4088.5 0.0011 9292.9225 4088.5 -0.0010 9293.0633 4089 0.0007 9293.0626 4089 -0.0000 [FIGURE 1] Figure 1. Light and color curves of VW Cep. [FIGURE 2] Figure 2. O-C diagram of VW Cep. [FIGURE 3] Figure 3. Variations of maxima and minima of VW Cep. I would like to express my hearty thanks to Prof. M. Kitamura and Dr. A. Okazaki for valuable suggestions and encouragement. Kikuichi ARAI Kuki-Hokuyo Senior High School, Kuki, Saitama, 346 Japan and JAPOA^1 Member References: Arai, K., 1991, IBVS, No. 3575 Glownia, Z., 1988, IBVS, No. 3258 Lloyd, C., Watson, J., Pickard, R. D., 1992, IBVS, No. 3704 Navratil, M., 1994, IBVS, No. 3997 Vinko, J., 1989, IBVS, No. 3291 Vinko, J., Gal, J., Szatmary, K., Kiss, L., 1993, IBVS, No. 3965 Wunder, E., Wieck, M., Kilinc, B., Gulmen, O., Tunca, Z., Evren, S., 1992, IBVS, No. 3760 1 JAPOA: Japan Amateur Photoelectric Observers Association