COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 3629 Konkoly Observatory Budapest 24 June 1991 HU ISSN 0374 - 0676 NEW TIMES OF MINIMA FOR THE EARLY-TYPE BINARIES V1331 Aql, V701 Sco AND MY Ser Three early-type eclipsing variables were measured in the UBV system by one of us (R.L.) with the ESO 50 cm telescope at La Silla in June 1990. In this note, the times of measured minima are discussed. V1331 Aql By now, only three times of minima were published for this B1 binary (see Mayer et al. 1991). A complete light curve containing another three minima was measured in Chile. The times of minima were calculated by the Kwee- van Woerden method. All known minimum times are collected in Table 1. New period has been calculated: Pri.Min. = HJD 2442610.0581 + 1.3641953d*E , +-1 the respective O-C values are given in Table 1. Table 1 HJD Error Epoch O-C Source 2400000+ (day) (day) 42610.0581 0 0 see Mayer et al.(1991) 42957.909 255 -0.0189 " " " " 47368.392 3488 +0.0211 " " " " 48062.7464 0.0003 3997 -0.0011 this paper 48066.8417 0.0006 4000 +0.0016 " " 48071.6125 0.0015 4003.5 -0.0022 " " It seems that the errors of the second and third minimum time cannot be as large as their O-C values would suggest, i.e., the period might be variable. Normal points of the new UBV light curve were published by Lorenz et al. (1991). [FIGURE 1] Fig. 1 V701 Sco: measurements of primary (top) and secondary (middle, bottom) minima, obtained in June 1990 at the ESO 50cm telescope V701 Sco Recently a photometric and spectrographic study of V701 Sco was published by Bell and Malcolm (1987). This study included also a discussion of the orbital period of the binary, and arrived at the ephemeris Pri.Min. = HJD 2446199.5059 + 0.76187645d*E , +-3 +-19 based on 8 photoelectric times of minima. In Table 2 we give the minimum times obtained in Chile; the measurements are plotted in Figure 1. The comparison star was HDE 317845, the same as used by Bell and Malcolm. The number of epochs and the O-C values correspond to the ephemeris given by these authors. We do not give a new ephemeris, since the O-C values are quite small; they however suggest that the present period has been shorter than 0.761876. The conclusion made by Bell and Malcolm, that the period of V701 Sco has remained nearly constant in the time interval covered by photoelectric Table 2 HJD Error Epoch O - C Source 2400000+ (day) (day) 48070.6727 0.0002 2456 -0.0016 this paper 48971.8152 0.0002 2457.5 -0.0019 " " 48072.5777 0.0002 2458.5 -0.0013 " " data (which is now about 24 years), is therefore confirmed, in spite of a discordant measurement by Bruton and Chambliss (1985). MY Ser No accurate minimum time has yet been published for this star. Among measurements by Davidge and Forbes (1988), there are several nights which cover down- or upward parts of minima, and which can be combined to calculate times of minima. Results for a secondary and a primary minimum are listed in Table 3. There is also given a secondary minimum time calculated from measurements obtained in the UBV system during one night in June 1990. The comparison star was HD 168112. The formal errors of the minimum times are small, however, asymmetries in the light curves are present and the real errors can be worse. Data in Table 3 suggest that the phase of the secondary minimum is 0.503; according to Davidge and Forbes, MY Ser is a semi-detached system, and in such a case the orbit should be circular. Therefore, we estimate the errors of the minimum times as 0.005d, and the resulting ephemeris is Pri.Min. = JD 2446231.612 + 3.32160d*E. +-5 +-1 Table 3 HJD Error Epoch O-C Source 24400000+ 46230.941 0.002 -0.5 -0.0107 (1) 46232.6125 0.0010 0 0 (1) 48067.7894 0.0008 552.5 -0.0071 this paper (1) calculated according to data by Davidge and Forbes (1988) REINALD LORENZ HORST DRECHSEL Dr. Remeis-Sternwarte Sternwartstr. 7 D-8600 Bamberg Germany PAVEL MAYER Dept. of Astronomy and Astrophysics Charles University Svedska 8 150 00 Praha 5 Czechoslovakia References: Bell, S.A., Malcolm, J.: 1987, Mon. Not. Roy. Astr. Soc., 226, 899. [BIBCODE 1987MNRAS.226..899B ] Bruton, J.R., Chambliss, C.R.: 1985, IBVS, No. 2805. Davidge, T.J., Forbes, D.: 1988, Mon. Not. Roy. Astr. Soc., 235, 797. [BIBCODE 1988MNRAS.235..797D ] Lorenz, R., Drechsel, H., Mayer, P.: 1991, IBVS, No. 3599. Mayer, P., Wolf, M., Tremko, J., Niarchos, P.G.: 1991, Bull. Astr. Inst. Czechosl., 42, No. 4. [BIBCODE 1991BAICz..42..225M ]