COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS NUMBER 805 Konkoly Observatory Budapest 1973 June 28 PHOTOELECTRIC OBSERVATIONS OF BETA LYRAE IN 1967 AND 1969 In this note two series of photoelectric observations of Beta Lyrae are presented, taken at the Hamburg Observatory in June-July 1967 and August-September 1969. The total of individual observations is 179, normal points are given in the table. The observed light curves remained rather fragmentary but it was possible to derive an epoch of primary minimum for each of the years. Later, the photometric Beta Lyrae program was discontinued as important, regular coverage of the light curve by several stations had been organized by the Dyer Observatory (Nashville, Tenn.) 1. Two-color observations in 1967 were carried out by Prof. A. Wachmann and the present writer, using the 60 cm reflector in Bergedorf. The instrumental b and v color are supposedly close to the UBV system. As comparison star HR 6997 was used, check star was 9 Lyrae. From 6 comparisons in as many nights, the magnitude difference between these stars turned out to Delta m = +0.179 +/- 0.003 in v, Delta m = -0.023 +/- 0.004 in b. (in the sense comp-check). The standard deviations correspond to a mean error of +/- 0.007 resp. +/- 0.009 mag. of a single observation; all observations were taken near culmination. On the basis of these observations the date of primary minimum can only be bracketed: it probably occurred between JD 2439677.2 and 2439677.3. This datum refers to E = 255, if we use the linear ephemeris of Wood and Walker (1). 2. For the 1969 set of observations the 1 m reflector was used, diaphragmed to 40 or 45 cm. The team of observers consisted of Messr. U. Gehlich, T. Herczeg, J. Prolss and R. Wehmeyer. These were 3-color measurements, the instrumental ubv system again following the UBV prescription. No color transformation formula was established but we notice that the reference stars indicated slightly different Delta m values: +0.174 +/- 0.0035 in v, -0.008 +/- 0.004 in b, -0.575 +/- 0.009 in u. (Again in the sense comp-check, 8 measurements in 7 nights.) This time the zenith distances of the observed stars were much greater than in 1967, resulting in the mean errors +/- 0.010, +/- 0.012 and +/- 0.025 mag. for a single v, b or u observation. The second series of measurements, especially the observations made on September 13 and 27, can define a more reliable epoch of minimum light: JD 2440479.04. Comparison with observations published by Lovell and Hall (2) reveals a difference of about three hours, our epoch being late. Part of this deviation may be ascribed to erratic changes in the light curve; such effects are clearly noticeable in the 1958 and 1959 campaign results, see Larsson-Leander (3). Also, the Chagrin Falls observations extended over two seasons and during this time, the rapid change of the period can shift the minimum epoch by about one hour. The Wood-Walker ephemeris gave residuals already in excess of 0.6 day. For the years around 1970, the linear ephemeris Min. I = JD 2440479.033 + 12.93386d E gives reasonably small O-C values. No doubt this formula too will soon prove its "ephemeral" character; for the present season, residuals of the order of 0.05d or 0.06d are to be expected. Table of observations (comp-var) JD 2439657.513 n = 5 b = 1.532 v = 1.617 658.502 4 1.611 1.700 660.502 4 1.920 2.013 665.501 4 1.600 1.719 676.509 4 1.216 1.373 677.506 4 0.924 1.082 685.501 2 1.80 1.91 C JD 2439694.448 n = 4 b = 1.848 v = 1.936 JD 2440448.435 n = 3 u = 1.917 b = 1.799 v = 1.881 451.380 4 1.928 1.877 1.979 452.390 2 1.41 1.40(5) 1.51 C 456.413 5 2.059 1.959 2.054 477.345 4 1.855 1.807 1.899 478.344 6 1.195 1.232 1.378 .496 4 1.146 1.168 1.296 492.338(5) 2 1.019 1.020 1.145 .378(5) 2 1.025 1.008 1.178 .421 2 1.090 1.061 1.195 C JD 2440493.351 n = 5 u = 1.749 b = 1.690 v = 1.768 C = measurements interrupted by clouds T. J. HERCZEG Department of Physics & Astronomy University of Oklahoma Norman, Oklahoma 73069 and Hamburger Sternwarte Hamburg - Bergedorf, Germany References: (1) Wood, D.B. and Walker, M.F. (1960) Ap. J. 131, 363. [BIBCODE 1960ApJ...131..363W ] (2) Lovell, L.P. and Hall, D.S. (1970) P.A.S.P. 82, 345. [BIBCODE 1970PASP...82..345L ] (3) Larsson-Leander, G. (1970) Vistas in Astronomy (ed. A. Beer), Vol. 12, 183-197. [BIBCODE 1970VA.....12..183L ]