COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2124 Konkoly Observatory Budapest 1982 April 16 HU ISSN 0374-0676 PHOTOELECTRIC OBSERVATION OF V 836 CYGNI The variability and eclipsing character of this system (BD +35d 4496 = HD 203470) was discovered by Strohmeier, Kippenhahn and Geyer (1956) who gave it the temporary designation BV 143. From the photographic light curve, Schmidt (1956) classified it as an Algol type variable. BV 143 was observed photoelectrically by Deinzer and Geyer (1959). According to these investigators the system was of Beta Lyrae type. Their light curve was very asymmetric in both minima and the second maximum was much brighter than the first maximum. In 1960 BV 143 was named as V 836 Cygni by Kukarkin, Efremov and Kholopov. Later the system was observed by Cester (1963) and Harris (1954, 1968). Cester and Harris analyzed the light curve using the Russell-Merrill method and gave the light elements. According to Harris (1968) the light elements are: Min I = JD(Hel) 24 26 547.5229 + 0.65 3410818d E +- 13 +- 81 p.e. We observed the system photoelectrically on six nights in 1981 with the 48 cm Cassegrain reflector at the Ege University Observatory using EMI 9781A photomultiplier and standard B, V filters. BD +35d 4461 and BD +35d 4460 were used as comparison and check stars, respectively. A total of 235 observational points were obtained in each colour. All the differential observations (comparison minus variable) were corrected for differential extinction with the conventional method. During the observations we obtained four primary and two secondary minima which are given in Table I. The O-C diagram of the system is given in Figure 1 using the light elements given in GCVS (1969). It can be seen from Figure 1 that the period of the system has started showing a decrease nearly since 1967. The first twelve points in Figure 1 are plotted from photographic and the others from photoelectric minima. All these points represent the primary minima. We assume that the period had no variation till 1967 so that the corrections in the light elements were done only with the photoelectric minima obtained after 1967. The revised light elements, JD Hel Min I = 24 44 853.4903 + 0.6534122d .E +- 2 +- 1 have been derived by the least squares method. [FIGURE 1] Table I: Times of minima of V 836 Cyg -------------------------------------------------------------- Hel.Min. Min. O-C_1 O-C_2 Filter -------------------------------------------------------------- 2444853.4904 I +0.0082 +0.0001 B 853.4900 I +0.0078 -0.0003 V 874.3997 I +0.0084 +0.0002 B 874.4001 I +0.0088 +0.0006 V 879.3013 II +0.0094 +0.0012 B,V 894.3340 II +0.0136 +0.0054 B 894.3305 II +0.0101 +0.0019 V 895.3097 I +0.0092 +0.0010 B 895.3076 I +0.0071 -0.0011 V 929.2879 I +0.0100 +0.0018 B 929.2875 I +0.0097 +0.0014 V [FIGURE 2] The O-C_1 values in. Table I are calculated with the light elements of GCVS (1969) and the O-C_2 values with the above-revised elements. The O-C diagram which is plotted with the revised elements is given in Figure 2. The light and colour curves are presented in Figure 3 where the phases have been calculated with the revised light elements. The shape of the light curve is similar to a Beta Lyrae type. The depth of secondary minima changes from night to night while the primary shows no variation. At the present time the light curves are not complete and more observations are needed. [FIGURE 3] This project is partly supported by the Scientific and Technical Research Council of Turkey. S. BOZKURT Ege University Observatory Bornova - Izmir - Turkey References: Cester, B., 1963, Oss. Astronomico de Trieste, No. 317 Deinzer, W., Geyer, E., 1959, ZfA, 47, 211 [BIBCODE 1959ZA.....47..211D ] Harris, A.J., 1964, M.S. Thesis, University of Pennsylvania Harris, A.J., 1968, A.J. 73, 164 [BIBCODE 1968AJ.....73..164H ] Kukarkin, B.V., Efremov, Yu.I., Kholopov, P.N., 1960, First Suppl. to the 2nd edition of the G.C.V.S., Moscow, pp. 33, 146, 201 Schmidt, H., 1956, Kl. Veroff. Remeis-Sternwarte Bamberg, Nr. 16 Strohmeier, W., Kippenhahn, R., Geyer, E., 1956, Kl. Veroff. Remeis- Sternwarte Bamberg, Nr. 15 ERRATUM A label in the paper "Observations of Early-type Ultra-short Period Variables" by L.A. Balona (I.B.V.S. No. 2120) is in error. This occurs in the figures where the star labeled HR 3462 should read HR 3467.