COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2100 Konkoly Observatory Budapest 1982 March 4 HU ISSN 0374-0676 PHOTOELECTRIC MINIMA AND LIGHT CURVES OF V 478 CYGNI V 478 Cygni (BD + 37d3890 = HD 193611) was discovered to be a binary by J.A. Pearce from a spectrogram obtained on September 29, 1947 (McDonald, 1948). McDonald (1948) investigated the system spectroscopically and determined the orbital elements from the radial velocity curve; and he also suggested that the system may be an eclipsing binary with the following light elements: Min I JD Hel = 24 32 458.777 + 2.8815d.E. +-878 From the spectroscopic and photometric elements Gaposchkin (1949) found that the system consists of two spherical, or very nearly spherical components which are identical in their physical characteristics and gave the light elements as, Min: JD 24 18 552.648 + 2.880921d.E. Popper and Dumont (1977) observed the system photoelectrically at Palomar and Kitt Peak Observatories and obtained its light curves. A neighbouring star to V 478 Cyg was apparently included in the Palomar observations because of the larger diaphragm used there than for the Kitt Peak observations. Thus the light curves were systematically different from each other. Koch et al. (1979) announced the system as a photometrically neglected eclipsing binary. The system was observed photoelectrically at the Ege University Observatory on 31 nights in the period of the observational season in 1981. The observations were made in yellow and blue colours with the 48 cm Cassegrain telescope equipped with an unrefrigerated EMI 9781 A photomultiplier tube and Johnson's standard B,V filters. A total of 1093 and 1084 individual points were obtained in B and V colours, respectively. BD + 37d3873 was used as comparison and BD + 37d3874 as check star. No evidence for the variability of the comparison star was found. All the observations were corrected for atmospheric extinction using the extinction coefficients determined from observations of the comparison star for each night. During all the observations the smallest diaphragm was used to eliminate the light of the neighbouring star to V 478 Cygni. Seven primary and three secondary minima were obtained in the observational season and are given in Table I. Table I Times of minima of V 478 Cygni ---------------------------------------- Hel Min JD Min Filter O-C ---------------------------------------- 24 44 777.4777 I B,V -0.0002 800.5236 I " -0.0006 813.5094 II " +0.0216 816.3893 II " +0.0207 826.4533 I " +0.0019 829.3318 I " -0.0004 849.4970 I " -0.0009 852.3781 I " -0.0005 862.481 II V +0.020 878.3065 I B,V +0.0008 ---------------------------------------- New light elements are determined using the above photoelectric primary minima by the method of weighted least squares as, Hel Min I JD = 24 44 777.4779 + 2.880795d.E. +-6 +-29 The light and colour curves are presented in Figure 1 where the magnitude differences between the comparison and variable stars have been plotted against the phases. The phases in Figure 1 and the O-C values in Table I were calculated with the above new light elements. The light curves show that the system is an Algol type eclipsing binary. [FIGURE 1] The phase of mid-secondary does not coincide with 0.5 phase. The phase shift of the secondary minima is about 0.0072 phi. Since there is no shift in the mid-primary, it clearly shows that the relative orbit is not circular but eccentric. The system varies about 0.395m and 0.385m at the primary, 0.380m and 0.365m at the secondary minimum in blue and yellow light, respectively. There is no variability in the colour curve. The shape of light curve confirms the results of Gaposchkin (1949). The solutions are in progress. This project is partly supported by the Turkish Scientific and Technical Research Council. C. SEZER, N. GUDUR and O. GULMEN Ege University Observatory Bornova - Izmir - Turkey References: Gaposchkin, S.: 1949, Astron.J. 54, 128. [BIBCODE 1949AJ.....54..128G ] Koch, R.H., Wood, F.B., Florkowski, D.R. and Oliver, J.P.: 1979 IBVS No. 1709. McDonald, J.K.: 1948, Astron.J. 54, 43. [BIBCODE 1948AJ.....54Q..43M ] Popper, D.M. and Dumont, P.J.: 1977, Astron.J. 82, 216. [BIBCODE 1977AJ.....82..216p ]