COMMISSIONS 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 3950 Konkoly Observatory Budapest 12 November 1993 HU ISSN 0374 - 0676 PHOTOELECTRIC MINIMA TIMES OF THE ECLIPSING VARIABLES AB ANDROMEDAE, 44i BOOTIS AND GO CYGNI The aim of the present report is to give the photoelectric minima times of AB And, 44i Boo and GO Cyg obtained from our observations made either at the Kryonerion Astronomical Station or at the Bucharest Observatory. The photoelectric observations of AB And were made during 1990 with the two-beam, multi-mode, nebular-stellar photometer of the National Observatory of Athens, Greece, attached to the 48-inch Cassegrain reflector at the Kryonerion Astronomical Station. While those of 44i Boo and GO Cyg were made during 1989, 1990 and 1993 with an EMI 9502 B type photocell, attached to the 50 cm telescope of the Bucharest Observatory. The filters used are in close accordance with the standard UBV and the reduction of the observations has been made in the usual way (Hardie. 1962). From our observations 5 new minima times were derived for AB And, 6 far 44i Boo and 3 for GO Cyg, which are presented in Tables I, II and III, respectively. The times of minima as well as the mean errors sigma have been computed using Kwee and Van Woerden's method (1956). Table I Photoelectric minima times of AB And ---------------------------------------------------------- Hel.JD (O-C)_I (O-C)_II (O-C)_III sigma Obs ---------------------------------------------------------- 2440000.+ 8173.3591 0.0734 0.0327 -0.0020 0.0003 R&R 8174.3509 0.0695 0.0289 -0.0059 0.0005 R&R 8176.3420 0.0693 0.0286 -0.0061 0.0006 R&R 8176.5104 0.0717 0.0310 -0.0037 0.0004 R&R ---------------------------------------------------------- where the residuals (O-C)_I, (O-C)_II and (O-C)_III have been calculated according to the following ephemeris formulae: Min I=2425502.11989+0.331886486d x E (Oosterhoff, 1950) Min I=2436109.578+0.33189122d x E (Kukarkin et al., 1969) and Min I=2436109.57928+0.33189215d x E (Kholopov et al., 1985) and they are the mean values of our B and V observations. From the O-C values, given in Table I for AB And, it is obvious that its period continues to change. A detailed study of its behaviour will appear elsewhere (Rovithis-Livaniou et al., 1994). Table II Photoelectric minima times of 44i Boo ------------------------------------------------------------- Hel.JD (O-C)_I (O-C)_II (O-C)_III sigma Obs Filter days days days ------------------------------------------------------------- 2440000.+ 9099.4042 0.0345 0.0015 -0.0159 0.0003 D V 9149.3581 0.0406 0.0074 -0.0102 0.0021 D U 9149.3664 0.0489 0.0157 -0.0018 0.0006 D V 9159.4094 0.0487 0.0156 -0.0021 0.0010 D U 9162.3508 0.0442 0.0110 -0.0066 0.0006 D U 9162.3503 0.0436 0.0105 -0.0072 0.0005 D V 9168.3732 0.0408 0.0075 -0.0102 0.0007 D U 9168.3729 0.0405 0.0072 -0.0105 0.0008 D B 9168.3740 0.0416 0.0083 -0.0094 0.0006 D V 9177.3478 0.0435 0.0102 -0.0076 0.0005 D U 9177.3482 0.0439 0.0106 -0.0071 0.0007 D B 9177.3479 0.0436 0.0103 -0.0075 0.0005 D V ------------------------------------------------------------- For 44i Boo the residuals (O-C)_I, (O-C)_II and (O-C)_III have been computed using the following ephemeris formulae, respectively: Min I=2439852.4903+0.2678159d x E (Duerbeck, 1975) Min I=2439852.4644+0.2678176d x E (Rovithis et al., 1990) and Min I=2443604.5880+0.26781856d x E (Oprescu et al., 1989) Since the O-C values for 44i Boo were found to be quite different for the various filters used, in Table II we give them separately and not a mean value, as we did in the case of AB Andromedae. Table III Photoelectric minima times of GO Cyg ------------------------------------------------ Hel.JD (O-C)_I (O-C)_II(O-C)_III sigma Obs days days days ------------------------------------------------ 2440000.+ 7802.3114 0.0255 0.0444 0.0116 0.0003 O&D 8176.2725 0.0221 0.0399 0.0060 0.0011 O&D 8180.2689 0.0307 0.0482 0.0146 0.0012 O&D ------------------------------------------------ In the case of GO Cygni the residuals (O-C)_I, (O-C)_II and (O-C)III have been computed according to the following ephemeris formulae, respectively: Min I=2446351.328+0.717763d * E (SAC, 1992) Min I=243393.40561+0.71776382d * E (Kholopov et al., 1985) and Min I=2445865.4056+0.71776707 * E (Sezer et al., 1985) and they are the mean values of our B and V observations. A detailed study of the period behaviour of GO Cygni will be made later on. Acknowledgement. This work was partly Supported by NATO, grant no. 921208/1993. P. ROVITHIS and G. OPRESCU H. ROVITHIS-LIVANIOU A. DUMITRESCU and Astronomical Institute, D.M. SURAN National Observatory of Athens Institutul Astronomie P.O. Box 20048 Academia Romana Athens, 11810 75212 Bucuresti 28 Greece Romania References: Duerbeck, H.W., 1975, IBVS, No. 1023 Hardie, R.H., 1962, in W. A. Hiltner (Ed.), Stars and Stellar Systems Vol II, "Astronomical Techniques", The Univ. of Chicago Press, Chicago Kholopov, P.N. et al., 1985, Fourth Edition of the GCVS, Moscow Kukarkin, B.V. et al., 1969, Third Edition of the GCVS, Moscow Kwee, K.K. and Van Woerden, H., 1956, Bull. Astr. Inst. Neth., 12, 327 [BIBCODE 1956BAN....12..327K ] Oosterhoff, P., 1950, Bull. Astr. Inst. Neth., 11, 217 [BIBCODE 1950BAN....11..217O ] Oprescu, G., et al., 1989, IBVS, No. 3368 Rovithis-Livaniou, H. Rovithis, P., Kalimeris, A., Oprescu, G., Dumitrescu, A., & Suran, D.M., 1994 A&A, (in press) Rovithis, P. and Rovithis-Livaniou, H., 1990, A&A Suppl. Ser., 86, 523 [BIBCODE 1990A&AS...86..523R ] SAC, 1992, Rocznik Astr. Obs. Krakowskiego, No. 63 Sezer, C., Gulmen, O. & Gudur, N., 1985, IBVS, No. 2743 [From IBVS 3998] ERRATUM In the No. 3950 issue of the IBVS one of the references was incorrectly given. On page 2, the third ephemeris is based on Oprescu et al. (1991) and the correct reference is: Oprescu, G., Suran, D. M., and Popescu, N., 1991, Inf. Bull. Var. Stars, No. 3560 G. OPRESCU