COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3575 Konkoly Observatory Budapest 12 March 1991 HU ISSN 0374 - 0676 PHOTOELECTRIC OBSERVATION OF VW CEPHEI IN R AND IR VW Cep (BD+75d0752) is a W UMa-type eclipsing binary remarkable for peculiar variation of its light curve for which Yamasaki (1982) suggested a spot model. So far observations in UBV have been often made by various authors (e.g., Abe 1982, Karimie 1983), but only few red and infrared observation have been published (e.g., Linnell 1982). Red and infrared observation of VW Cep would be important to study the validity of the spot model. The present observation is to consolidate the red and infrared data of VW Cep. Our observations were carried out during nine nights in December 1989 and January 1990 with an SSP-3 detector attached to a 28-cm (f=2,800mm) Schmidt-Cassegrain type telescope. Two filters with peak transmission at 670nm for red and 880nm for infrared were used throughout the observations. BD+74d889 was used as the comparison star, which is the same one as used in the previous works (e.g., Karimie 1983, Linnell 1982). The present observations could cover four primary and two secondary minima, as shown in Table I, where the O-C values were calculated with the ephermeris : Min I = JD Hel 2444157.4131 + 0.27831460d * E which has been taken from the General Catalogue of Variable Stars (1985). The obtained light and color curves in R and IR are shown in Figure 1, where the light curve is shown by individual observations while the color curve in R-IR by normal points. It is found that the general feature of the light curve is quite consistent with the previous one by Linnell (1982). Table II shows values of DeltaR, DeltaIR and Delta(R-IR) of VW Cep obtained from the present observation. In this table the corresponding values taken from Linnell's (1982) work are also shown in parentheses, as a comparison. Table III shows amplitudes of Max I - Max II, Max I - Min I and Max II - Min II in DeltaR, DeltaIR and Delta(R-IR), respectively. The numbers in parentheses are the ones read from Table 4 of Linnell's (1982) paper. I would like to express my hearty thanks to JAPOA members who kindly helped during the observation as well as in the subsequent reduction work. Table 1. The times of observed minima of VW Cep Hel.J.D s.d. E filter O-C 2440000+ 7892.0693 +-0.0002 13419 R -0.0474 7892.0698 +-0.0001 13419 IR -0.0469 7895.9649 +-0.0001 13933 R -0.0482 7895.9641 +-0.0002 13933 IR -0.0490 7896.9916 +-0.0002 13436.5 R -0.0456 7896.9403 +-0.0001 13436.5 IR -0.0469 7899.0270 +-0.0001 13444 R -0.0476 7899.0274 +-0.0001 13444 IR -0.0472 7905.0135 +-0.0003 13465.5 R -0.0449 7905.0121 +-0.0001 13465.5 IR -0.0463 7912.9418 +-0:0001 13494 R -0.0485 7912.9439 +-0.0001 13494 IR -0.0464 Table 2. DeltaR, DeltaIR and Delta(R-IR) values of VW Cep at maxima and minima. Phase DeltaR DeltaIR Delta(R-IR) Maxima I -0.633+-0.017 (-0.650) -0.743+-0.018 (-0.730) 0.110 (0.133) minima I -0.262+-0.020 (-0.280) -0.419+-0.010 (-0.393) 0.157 (0.163) Maxima II -0.598+-0.008 (-0.615) -0.720+-0.022 (-0.703) 0.122 (0.135) minima II -0.358+-0.004 (-0.348) -0.499+-0.006 (-0.435) 0.141 (0.143) Table 3. Three amplitudes of Max I - Max II, Max I - Min I and Max II - Min II in DeltaR, DeltaIR and Delta(R-IR). Phase DeltaR DeltaIR Delta(R-IR) Max I - Max II -0.035 (-0.035 ) -0.023(-0.027) -0.012(-0.002) Max I - Min I -0.371 (-0.371 ) -0.324(-0.337) -0.097(-0.030) Max II- Min II -0.242 (-0.267 ) -0.221(-0.268) -0.021(-0.008) [FIGURE 1] Figure 1. R and IR Light curves (lower) of VW Cep shown by individual observations and the corresponding color curve (upper) by the mean of several individual ones. In particular, my sincere gratitude is due to Prof. M. Kitamura of National Astronomical Observatory for his valuable suggestion and constant encouragement throughout the work. Thanks are also extended to Messrs. S. Ohmori, O. Ohshima and Y. Ito for useful advice. KIKUICHI ARAI Member of Japan Amateur Photoelectric Observers Association (JAPOA) and Kuki-Hokuyo Senior High School Kukihon 837-1, Kuki City, Saitama Prefecture, Japan 346. References: Abe, T.: 1982, I.B.V.S., No. 2108. Karimie, M.T.: 1983, Astrophys. Space Sci., 92, 53. [BIBCODE 1983Ap&SS..92...53K ] Kholopov, P.N. (Editor-in-Chief): 1985, General Catalogue of Variable Stars, 4th edition, Moscow, Nauka Publishing House. Linnell, A.P.: 1982, Astrophys. J. Suppl., 50, 85. [BIBCODE 1982ApJS...50...85L ] Yamasaki, A.: 1982, Astrophys. Space Sci., 85, 43. [BIBCODE 1982Ap&SS..85...43Y ]