COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2545 Konkoly Observatory Budapest 5 July 1984 HU ISSN 0374-0676 TIMES OF MINIMA OF ECLIPSING VARIABLES - III This bulletin lists times of minima determined at this observatory in 1980, 1981 and 1983, as a continuation of the program for which results were previously published in I.B.V.S. No. 844 (1973) and I.B.V.S. No. 1379 (1978). The present observations were obtained with a larger telescope of 0.5 m aperture and with a new photometer designed and constructed by J.R. Stilburn. This photometer provides automatic sky subtraction by means of a rocking mirror, and by advancing the filter wheel several (normally 10) full cycles for each integration, permits essentially simultaneous observations in several colours. For the present observations a set of Johnson UBV filters was used, and times of minima determined independently for each of the three filters. As before, these were obtained by the method of Kwee and van Woerden Table I Observed Times of Minima Star HJD E O-C Observer [2,440,000+] (days) KO Aql 4450.7980 +- .0006 1430 .0308 F 5524.8317 +- .0008 1805 .0558 F OO Aql 4460.8016 +- .0010 7108.5 .0166 D 4476.7681 +- .0009 7140 .0193 B 4832.7879 +- .0006 7842.5 .0214 F 44i Boo 4366.7971 +- .0010 21856 .0318 D 4390.9032 +- .0022 21946 .0346 D 4409.7855 +- .0015 22016.5 .0360 B 4811.7794 +- .0035 23517.5 .0406 S 5473.8187 +- .0008 25989.5 .0430 G 5476.9019 +- .0006 26001 .0463 G 5477.8383 +- .0006 26004.5 .0453 G 5478.7745 +- .0009 26008 .0442 F 5488.8162 +- .0011 26045.5 .0429 G ZZ Boo 4363.8527 +- .0016 1161.5 .0228 S RZ Cas 4470.8530 +- .0008 12211 -.0020 F 4831.8169 +- .0001 12513 -.0028 S VW Cep 4427.7968 +- .0008 18192.5 .0165 D 4455.7641 +- .0020 18293 .0132 S 4455.9072 +- .0025 18293.5 .0172 S 4457.8538 +- .0028 18300.5 .0156 F 4470.7931 +- .0005 18347 .0133 F Table I (cont.) Star HJD E O-C Observer [2,440,000+) (days) VW Cep 4788.7666 +- .0007 19489.5 .0134 F 4812.8423 +- .0005 19576 .0149 F 4822.8616 +- .0005 19612 .0149 F 4824.8097 +- .0006 19619 .0148 F 4834.8279 +- .0010 19655 .0137 F 5507.7873 +- .0011 22073 .0105 S 5562.7544 +- .0005 22270.5 .0107 F 5562.8940 +- .0013 22271 .0111 F MR Cyg 4480.7613 +- .0012 6609.5 .0007 D 4833.7777 +- .0012 6820 .0015 S V1073 Cyg 5568.8845 +- .0010 8775.5 -.0028 G AI Dra 4371.7552 +- .0011 5695 -.0069 F 4769.7619 +- .0006 6027 -.0068 F 5478.8653 +- .0061 6618.5 -.0026 F 5481.8597 +- .0006 6621 -.0052 F TW Dra 4360.8447 +- .0012 2074 .0228 F S Equ 5544.9246 +- .0009 2205 .0420 F Z Her 4413.8677 +- .0008 7846 .0015 D 4433.8286 +- .0008 7851 -.0016 D RX Her 4813.8251 +- .0014 6990.5 .0030 F 4821.8271 +- .0006 6995 .0015 S 4829.8294 +- .0008 6999.5 .0002 S TX Her 4362.8122 +- .0009 6815 .0122 F 4809.7966 +- .0007 7032 .0181 S 5499.8294 +- .0023 7367 .0148 G 5532.7877 +- .0019 7383 .0161 G AK Her 5480.8681 +- .0011 16486.5 -.0041 G CM Lac 4446.8435 +- .0003 10856 -.0022 F 4458.8775 +- .0012 10863.5 -.0034 F 4828.7630 +- .0003 11094 .0007 F 5571.7352 +- .0004 11557 .0008 G FL Lyr 4459.7830 +- .0011 2482 .0067 S 5572.8218 +- .0010 2993 .0104 G U Oph 4371.9307 +- .0008 21517.5 -.0049 F 4408.8336 +- .0007 21539.5 -.0036 B 4429.8037 +- .0010 21552 -.0003 D 4793.7895 +- .0008 21769 .0014 S 5479.8250 +- .0009 22178 .0024 S V502 Oph 4370.8684 +- .0007 10434.5 -.0044 F V566 Oph 4406.8073 +- .0007 6276 .0092 D 4448.7922 +- .0013 6378.5 .0055 F 4780.8121 +- .0005 7189 .0075 S 4781.8357 +- .0005 7191.5 .0070 F 5512.8463 +- .0006 8976 .0049 F 5513.8700 +- .0007 8978.5 .0045 G EE Peg 4475.8140 +- .0014 1960 .0173 D 5546.8202 +- .0025 2367.5 .0288 G 5563.8916 +- .0016 2374 .0168 G 5567.8399 +- .0039 2375.5 .0228 G U Sge 4827.8181 +- .0002 8193 -.0036 F Observers: B = D.J. Barlow D = P.A. Delaney F = D.W. Forbes G = J. Gagne S = C.D. Scarfe (BAN 12, 327, 1956), the program was modified in 1983 for interactive use by one of us (D.W.F.). The results listed in Table I are averages of the minima from each colour (excluding U if it was strongly discordant), and the uncertainties are the larger of a. the root-mean-square value of the errors determined by the program for each colour b. the standard error of one determination from the interagreement between the times of minimum in each colour. The ephemerides used to calculate O-C were the same as those used in I.B.V.S. No. 844 and No. 1379. For stars not previously observed ephemerides are given in Table II. For TX Her the ephemeris in I.B.V.S. No. 1379 is incorrect, it should read P.Min. = 2430325.2006 + 2.05980915 E. Remarks on individual stars follow the table. Table II Ephemerides Star HJD Period R e f e r e n c e s [2,400,000+] KO Aql 40355.2140 2.8640232 Hayasaka, PASJ 31,271,1979 V1073 Cyg 38672.5816 0.7858597 Kondo, AJ 71, 54, 1966 TW Dra 38539.4457 2.8068352 Pohl, IBVS 443,1970 S Equ 37968.3438 3.436072 Plavec, BAC 15,25,1964 FL Lyr 39053.6060 2.17815081 Monske, IBVS 119,1965 V502 Oph 39639.9431 0.45339304 Binnendijk, AJ 74,222,1969 Notes on individual systems: 1. KO Aql Our observations and those of Olson (I.B.V.S. No. 1938, 1981) and Margrave (I.B.V.S. No. 1869, 1980; I.B.V.S. No. 1930, 1981; I.B.V.S. No. 2086, 1982; I.B.V.S. No. 2292, 1983) all indicate that since 1979 the rate of increase in the period has been less than found from earlier data by Hayasaka (1979), whose ephemeris includes the term + 2.00 x 10^-8 E^2, 2. OO Aql Our observations show increasing positive residuals from the ephemeris of Herczeg (I.B.V.S. No. 699, 1972). This trend may be accelerating, according to the recent observation of Pohl et al., (I.B.V.S. No. 2385, 1983). 3. 44i Boo The residuals from the ephemeris of Pohl (I.B.V.S. No. 209, 1967) continue to increase, possibly at an accelerating rate, 4. VW Cep Our results, together with others in the literature, indicate little departure from the period of Scarfe and Brimacombe (AJ 76, 50, 1971) that cannot be interpreted as a light-time effect in the triple system (Hershey, AJ 80, 662, 1975). The most recent observations, however, do suggest a new decrease in the period. The observations of Mahdy and Soliman (I.B.V.S. No. 2153, 1982) are anomalous, giving large positive residuals. 5. TX Her The most recent minima favour the quadratic ephemeris of van Hamme (A. and Ap. 107, 409, 1982) over his linear and periodic ephemerides. 6. V566 Oph The last entry in Table I of I.B.V.S. No. 1379 should have E = 2812. Our observations and those of Pohl and Gulmer (I.B.V.S. No. 1924, 1981) and Pohl et al., (I.B.V.S. No. 2385, 1983) disagree with those of Mahdy and Soliman (I.B.V.S. No. 2154, 1982) and Niarchos (I.B.V.S. No. 2451, 1983) in showing positive residuals from the ephemeris given in I.B.V.S. No. 1379. C.D. SCARFE D.W. FORBES P.A. DELANEY J. GAGNE Climenhaga Observatory University of Victoria Victoria, B.C., Canada