COMMISSIONS 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS Number 3981 Konkoly Observatory Budapest 26 January 1994 HU ISSN 0374 - 0676 BV LIGHT CURVES OF BY Dra IN 1993 Photometry in BV was obtained for the spotted star BY Dra (BD +51d2402) during 1993 at Bucharest Observatory. The observations were carried out with a 50 cm Cassegrain telescope during the period 10 July-27 November 1993, on 23 nights. An EMI 9502B unrefrigated photomultiplier and filters V (Schott 1mm GG11) and B (Schott 1mm BG12+Schott 1mm GG13) were used. The data were obtained by a paper milli-voltmeter recorder. Our comparison star was HD 172268, V=7.89, B-V=1.27 (Rodono et al., 1986). Mean JD, V magnitudes and B-V colours are presented in Table I and Figure 1. The phases are calculated using the ephemeris given by Rodono et al. (1986). Min=J.D. 2438983.612+3.836d x E No significant B-V variation is observed, the mean value being 1.20m. However, at minimum the star seems to be a little redder, which is consistent with the maximum visibility of the spot at that phase. From our observations it is difficult to determine the light curve amplitudes precisely. A rough estimate shows that the amplitudes lie around of 0.08m in both colours. The observed minimum is at phase ~0.5 with respect to the ephemeris used by us. Comparing our data with those obtained in 1991 by Panov and Ivanova (1993) our observations indicate no spectacular changes in the light curves. However, a mean brightness increase of about 0.15m is evident in both colours. [FIGURE 1] Figure 1. V, B-V light curves of BY Dra obtained at Bucharest Observatory during the period July-November, 1993. Table 1 Photometric observations of BY Dra (N,sigma_V,sigma_B represent the number of individual points which form the mean value, and average standard deviations in V and B respectively). ------------------------------------------------------- JD N Phase V B-V sigma_V sigma_B ------------------------------------------------------- 2449000.0+ 178.4417 3 0.6717 8.040 1.205 .004 .012 206.3179 1 0.9387 8.008 1.210 - - 212.3063 3 0.5000 8.087 1.207 .001 .008 213.3208 3 0.7643 8.034 1.194 .010 .008 215.2950 2 0.2791 8.048 1.222 .009 .001 217.3213 2 0.8073 8.035 1.208 .010 .017 217.4138 3 0.8315 8.055 1.189 .011 .025 220.3194 1 0.5888 8.075 1.190 - - 223.2916 3 0.3636 8.075 1.181 .009 .017 223.3229 4 0.3717 8.064 1.197 .015 .009 230.2846 4 0.1866 8.059 1.202 .004 .012 242.3333 2 0.3276 8.093 1.165 .007 .017 245.3054 1 0.1024 8.046 1.190 - - 247.2396 3 0.6066 8.067 1.215 .006 .008 248.2917 2 0.8800 8.059 1.177 .008 .010 288.1875 5 0.2812 8.052 1.223 .007 .007 289.1870 5 0.5419 8.079 1.198 .011 .030 290.1804 5 0.8008 8.056 1.183 .010 .018 292.2150 2 0.3313 8.040 1.191 .016 .022 300.1754 4 0.4064 8.061 1.181 .007 .011 304.2000 1 0.4556 8.077 1.212 - - 317.1666 2 0.8357 8.059 1.182 .018 .007 319.1660 4 0.3571 8.051 1.178 .014 .005 -------------------------------------------------------- A. DUMITRESCU G. OPRESCU and F. DONEA Astronomical Institute of the Romanian Academy, Bucharest Observatory str. Cutitul de Argint 5, Bucharest 28 Romania References: Panov, K. P., Ivanova, M. S.: 1993, Astrophys. Sp. Sci., 199, 265 [BIBCODE 1993Ap&SS.199..265P ] Rodono, M., Custispoto, G., Catalano, S., Byrne, P. B., Doyle, J. G., Buttler, C. J., Andrews, A. D., Marilli, E., Linsky, J. L., Scaltriti, F., Busso, M., Cellino, A., Hopkins, J. L., Okazaki, A., Hayashy, S. S., Zeilik, M., Helston, R., Henson, G., Smith, P. and Simon, T.,: 1966, A & A, 165, 135 [BIBCODE 1986A&A...165..135R ]