COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 3293 Konkoly Observatory Budapest 21 February 1989 HU ISSN 0374 - 0676 UBVR PHOTOMETRY OF DI HERCULIS The first photoelectric observations of DI Her (HD 175227, B4V + B5V, P= 10.55d) were made in 1963 (Semeniuk, 1968). Martynov and Khaliullin (1978, 1980) have determined the photometric elements and apsidal motion period using their own UBV measurements. A significant discrepancy between the observed and the theoretically expected apsidal motion rate was found. To get more precise parameters of DI Her, new multicolour observations were carried out at the Tian-Shan (altitude 3000 m) and Moscow Observatories in 1986-1987. The 48 cm reflector with the WBVR photometer (EMI 9863) was used in Tian-Shan and the 70 cm reflector with UBV photometer (PMT-79, Soviet) vas used in Moscow. "V" bands of both photometers are close to each other. BD +24d3555 served as the standard star, and BD +24d3556 as control. Observations were corrected for the atmospheric extinction and reduced to the standard WBVR system. WBVR standards HD 174262 and HD 168913 (Khaliullin et al. 1985) were used to derive the stellar magnitudes and colours of the comparison stars and the variable. Table I presents these data. Table I. Stellar magnitudes W B V R W-B B-V B-R BD +24d3555 8.309 8.718 8.600 8.506 -0.409 0.118 0.212 +-5 +-4 +-3 +-5 BD +24d3556 9.701 9.704 9.496 9.363 -0.003 0.208 0.341 +-9 +-8 +-6 +-9 DI Her plateau 7.708 8.486 8.397 8.310 -0.778 0.089 0.176 +-5 +-4 +-3 +-5 Min I 8.474 9.217 9.103 9.011 -0.743 0.107 0.206 +-7 +-5 +-4 +-6 Min II 8.229 9.056 8.976 8.892 -0.827 0.080 0.164 +-6 +-4 +-3 +-5 Table II. Moments of photoelectric minima of DI Her JD hel E O-C References Min I 2438245.3838 -865 -0.00004 Semeniuk 1968 38308.6847 -859 -0.00014 " 42233.3476 -487 0.00026 Martynov, Khaliullin 1980 42602.605 -452 0.002 Koch 1977 42623.7035 -450 -0.00005 " 43309.467 -385 0.0025 Guinan, Maloney 1985 45883.7069 -141 0.001 " 45894.2519 -140 -0.0037 " 46643.31758 - 69 0.00003 Khodykin, Volkov 47371.27909 0 -0.00005 " 47424.0300 5 0.00002 " 47445.13045 7 0.00014 " Min II 2438306.2454 -860 0.0003 Semeniuk 1968 40363.5280 -665 -0.0011 Battistini et al. 1974 40511.2314 -651 -0.0002 Martynov, Khaliullin * 41882.7545 -521 0.0001 Koch 1977 42642.366 -449 -0.0009 Martynov, Khaliullin * 42937.7685 -421 -0.003 Koch 1977 43264.8256 -390 -0.0017 " 43296.4789 -387 0.001 Ebersberger et al. 1978 43676.2843 -351 0.0002 Guinan, Maloney 1985 43718.4845 -347 -0.0002 Martynov, Khaliullin * 44024.4399 -318 0.00004 Pohl, Gulmen 1981 45807.4195 -149 0.0001 Guinan, Maloney 1985 45944.5734 -136 0.0017 " 46535.3815 - 80 0.0001 Khodykin,Volkov 46630.3333 - 71 0.00013 " ** 46651.4332 - 69 -0.0002 Diethelm 1986 47263.3434 - 11 -0.00016 Khodykin, Volkov 47432.1462 5 -0.00015 " * - found by Guinan and Maloney (1985) ** - found here on the Metlov's observations (Crimea) We have obtained a new linear ephemeris for DI Her using our eight minima in V band in addition to all known photoelectric times of minima (see Table II): Min I J.D.hel. = 2447371.27914 + 10.5501680d E +-8 +-2 Min II J.D.hel. = 2447379.39548 + 10.5501749d E +-9 +-2 EII-EI = 8.1163d = 0.76931p, DeltaP = PII-PI = 0.0000069d = 0.60s +-1 +-1 +-2 +-2 Assuming that the period difference DeltaP is caused only by the periastron advance, we found from Roudkjobing's relationship (1959) the apsidal motion period U = 29300 +- 900 years, in agreement with the value yielded by Martynov and Khaliullin (1978). We thank Dr. V.G. Metlov for presenting his observational data before publication. S.A. KHODYKIN and I.M. VOLKOV Sternberg Astronomical Institute Moscow, U.S.S.R. References: Battistini, P., Bonifazi, A., and Guarnieri, A. 1974, IBVS No. 951. Diethelm, R. 1986, BBSAG Bull., No. 81. Ebersberger, J., Pohl, E., and Kizilirmak, A. 1978, IBVS No. 1149. Guinan, E.F., and Maloney, F.P. 1985, Astron. J., 90, 8. [BIBCODE 1985AJ.....90.1519G ] Khaliullin, Kh.F., Mironov, A.V., and Moshkalev, V.G. 1985, Astrophys. Space Sci., 111, 291. [BIBCODE 1985Ap&SS.111..291K ] Koch, R.B. 1977, Astron. J., 82, 653. [BIBCODE 1977AJ.....82..653K ] Martynov, D.Ya., and Khaliullin, Kh.F. 1978, Astron. Circ. USSR, No. 1016. [BIBCODE 1978ATsir1016....1M ] Martynov, D.Ya., and Khaliullin, Kh.F. 1980, Astrophys. Space Sci., 71, 1. [BIBCODE 1980Ap&SS..71..147M ] Pohl, E., and Gulmen, O. 1981, IBVS, No. 1924. Roudkjobing, M. 1959, Ann. Aph., 22, 111. [BIBCODE 1959AnAp...22..111R ] Semeniuk, I. 1968, Acta. Astr., 18, 1. [BIBCODE 1968AcA....18....1S ]